PG-08 Diagnostics and Trouble Shooting Guide

Manual Diag 2012 Diagnostic Trouble shooting GM Engines

Buck’s Engines

Diagnostic Guide

PG-08 Diagnostics and Trouble Shooting

Guide – GM Engines

Emission-Certified

Natural Gas Fuel Systems

March 2012

Manual Diag 2012

Buck’s Engines i


Contents

R

EGULATORY

C

OMPLIANCE

.........................................................................

Electromagnetic Compatibility (EMC) .................................................................... iv

Electrostatic Discharge Awareness ................................................................... iv

C

HAPTER

6.

B

ASIC

T

ROUBLESHOOTING

...................................................... 4

Preliminary Checks .............................................................................................. 4

Basic Troubleshooting ......................................................................................... 5

Intermittents .................................................................................................... 5

Surges and/or Stumbles ................................................................................. 6

Engine Cranking but Will Not Start / Difficult to Start ...................................... 7

Lack of Power, Slow to Respond / Poor High Speed Performance /

Hesitation During Acceleration ........................................................................ 9

Detonation / Spark Knock ............................................................................. 11

Backfire ......................................................................................................... 12

Dieseling, Run-on ......................................................................................... 12

Rough, Unstable, Incorrect Idle, or Stalling .................................................. 13

Cuts Out, Misses .......................................................................................... 15

Poor Fuel Economy / Excessive Fuel Consumption Natural Gas Exhaust

Smell ............................................................................................................. 16

High Idle Speed ............................................................................................ 17

Excessive Exhaust Emissions or Odors ....................................................... 18

Diagnostic Aids for Rich / Lean Operation .................................................... 19

Chart T-1 Restricted Exhaust System Check ............................................... 20

C

HAPTER

7.

A

DVANCED

D

IAGNOSTICS

...................................................... 21

Reading Diagnostic Fault Codes ...................................................................... 21

Displaying Fault Codes (DFC) from SECM Memory ........................................ 21

Clearing Fault (DFC) Codes ............................................................................... 21

Fault Action Descriptions .............................................................................. 21

Fault List Definitions ...................................................................................... 22

Table 1. Fault List Definitions........................................................................ 22

Table 2. Diagnostic Fault Codes (Flash Codes) ........................................... 29

C

HAPTER

8.

P

ARTS

D

ESCRIPTION

............................................................. 44

Fuel System Components ................................................................................. 44

CA225 Mixer ........................................................................................................ 45

Maxitrol R600S Regulator .................................................................................. 47

A

PPENDIX

................................................................................................ 48

Abbreviations ...................................................................................................... 48

Buck’s Engines ii


List of Figures

Figure 13. SECM Wiring Diagram for GM 3.0L Natural Gas System ..................... 3

Figure 26. Installing Exhaust Backpressure Tester .............................................. 20

Figure 27. CA225 Mixer Exploded View ............................................................... 46

Buck’s Engines iii


Electromagnetic Compatibility (EMC)

All PG-08 active electronic components manufactured by the Woodward

Governor Company have been developed and individually tested for electromagnetic compatibility using standardized industry methods under laboratory test conditions. Actual EMC performance may be adversely affected by the wiring harness design, wire routing, the surrounding structure, other EMC generating components, and other factors that are beyond the control of the

Woodward Governor Company. It is the responsibility of the vehicle and/or application manufacturer to confirm that the overall system's EMC performance is in compliance with all standards that they wish to apply for their particular use.

Electrostatic Discharge Awareness

All electronic equipment is static-sensitive, some components more than others.

To protect these components from static damage, you must take special precautions to minimize or eliminate electrostatic discharges.

Follow these precautions when working with or near the control.

1. Before doing maintenance on the electronic control, discharge the static electricity on your body to ground by touching and holding a grounded metal object (pipes, cabinets, equipment, etc.).

2. Avoid the build-up of static electricity on your body by not wearing clothing made of synthetic materials. Wear cotton or cotton-blend materials as much as possible because these do not store static electric charges as much as synthetics.

3. Keep plastic, vinyl, and Styrofoam materials (such as plastic or Styrofoam cups, cup holders, cigarette packages, cellophane wrappers, vinyl books or folders, plastic bottles, and plastic ash trays) away from the control, the modules, and the work area as much as possible.

CAUTION—ELECTROSTATIC DISCHARGE

To prevent damage to electronic components caused by improper handling, read and observe the precautions in Woodward manual

82715, Guide for Handling and Protection of Electronic Controls,

Printed Circuit Boards, and Modules.

Buck’s Engines iv

Manual 2012 Diag

DIAGRAM NOTES

Diagnostic Trouble shooting GM Engines

NOTE #1

Wire sizes are in AWG.

NOTE #2

All wire sizes are 18 AWG unless otherwise noted.

NOTE #3

All connector terminations are shown on wire side—not terminal side.

Refer to your CAN device documentation for proper CAN network configuration and use of termination

4

resistor. Also refer to ISO 11898-2 for CANBus criteria and SAE J1939 protocol for standard CAN restrictions.

5

XDRG Pin B1 and DRVG Pins A16, B17 should not be connected in the harness.

6

Pre-cat 02 sensor and post-cat 02 sensor signal ground wires must be electrically isolated from heater ground wires. Signal ground wires must go to XDRG and heater ground wires must go to DRVG.

7

Pre-cat 02 sensor and post-cat 02 sensor signal ground wire splices must be within 6” (152.4 mm) of

SECM-48.

All XDRG wires should be routed such that the splices are as close as possible to the SECM-48.

8

TERMINAL CONNECTIONS

Buck’s Engines 2

Manual 2012 Diag Diagnostic Trouble shooting GM Engines

Figure 13. SECM Wiring Diagram for GM 3.0L Natural Gas System

DWG NO. 9930-1095



Chapter 6.

Basic Troubleshooting

Preliminary Checks

PG-08 systems are equipped with built-in fault diagnostics. Detected system faults can be displayed by the

Malfunction Indicator Lamp (MIL) and are covered in Chapter 7, Advanced Diagnostics. However, items such as fuel level, plugged fuel lines, clogged fuel filters, and malfunctioning pressure regulators may not set a fault code and usually can be corrected with the basic troubleshooting steps described on the following pages.

If engine or drivability problems are encountered with your PG-08 system, perform the checks in this section before referring to Advanced Diagnostics.

NOTE: Locating a problem in a natural gas engine is done exactly the same as with a gasoline engine.

Consider all parts of the ignition and mechanical systems as well as the fuel system.

BEFORE STARTING . . .

1. Determine that the SECM and MIL light are operating. Verify operation by keying on engine and checking for flash of MIL light.

When the ignition key is turned on, the MIL will illuminate and remain on until the engine is started.

Once the engine is started, the MIL lamp will go out unless one or more fault conditions are present. If a detected fault condition exists, the fault or faults will be stored in the memory of the small engine control module (SECM). Once an active fault occurs the MIL will illuminate and remain ON. This signals the operator that a fault has been detected by the SECM.

2. Determine that there are no diagnostic codes stored, or there is a diagnostic code but no MIL light.

VISUAL/PHYSICALCHECK

Several of the procedures call for a “Careful Visual/Physical Check” which should include:

• SECM grounds for being clean and tight

• Vacuum hoses for splits, kinks, and proper connection.

• Air leaks at throttle body mounting and intake manifold

• Exhaust system leaks

• Ignition wires for cracking, hardness, proper routing, and carbon tracking

• Wiring for pinches and cuts

Also check:

• Connections to determine that none are loose, cracked, or missing

• Fuel level in vehicle is sufficient

• Fuel is not leaking

• Battery voltage is greater than 11.5 volts

• Steering, brakes, and hydraulics are in proper condition and vehicle is safe to operate

NOTE

The Visual/Physical check is very important, as it can often correct a problem without further troubleshooting and save valuable time.



Basic Troubleshooting

Intermittents

An intermittent fault is the most difficult to troubleshoot since the MIL flashes on at random, causing uncertainty in the number of flashes or the conditions present at the time of the fault. Also, the problem may or may not fully turn “ON” the MIL light or store a code.

Therefore, the fault must be present or able to be recreated in order to locate the problem. If a fault is intermittent, use of diagnostic code charts may result in the unnecessary replacement of good components.

CORRECTIVE ACTION

Most intermittent problems are caused by faulty electrical connections or wiring.

Perform careful visual/physical check for:

•

Poor mating of the connector halves or terminal not fully seated in the connector body (backed out)

•

Improperly formed or damaged terminal. All connector terminals in problem circuit should be carefully reformed or replaced to insure proper contact tension

•

Loose connections or broken wires

•

Poor terminal to wire connection crimp

If a visual/physical check does not find the cause of the problem, perform the following:

(1) Drive the vehicle with a voltmeter or “Service” tool connected to a suspected circuit. Check if circuit is active and signal is reasonable.

(2) Using the “Service” tool, monitor the input signal to the SECM to help detect intermittent conditions.

(3) An abnormal voltage, or “Service” reading, when the problem occurs, indicates the problem may be in that circuit.

(4) If the wiring and connectors check OK, and a diagnostic code was stored for a circuit having a sensor, check sensor.

An intermittent “Service Engine Soon” light with no stored diagnostic code may be caused by:

•

Ignition coil shortage to ground and arcing at spark plug wires or plugs

•

MIL light wire to ECM shorted to ground

•

SECM grounds (refer to SECM wiring diagrams).

Check for improper installation of electrical options such as lights, 2-way radios, accessories, etc.

EST wires should be routed away from spark plug wires, distributor wires, distributor housing, coil and generator. Wires from SECM to ignition should have a good connection.



Basic Troubleshooting (cont’d.)

Surges and/or Stumbles

Engine power varies under steady throttle or cruise. Feels like the vehicle speeds up and slows down with no change in the acceleration pedal.

PRELIMINARY CHECKS

Perform the visual checks as described at start of “ Basic Troubleshooting” chapter.

Be sure driver understands vehicle operation as explained in the operator manual.

PROBABLE CAUSE CORRECTIVE ACTION

Oxygen sensor malfunction

Fuel system malfunction

The fuel management should maintain a stoichiometric air-fuel ratio under all steady state operating conditions following engine warmup.

Failure of the Pre-catalyst O2 sensor should cause an O2 sensor fault that can be diagnosed with the

MIL lamp or Service Tool.

NOTE: To determine if the condition is caused by a rich or lean system, the vehicle should be driven at the speed of the complaint. Monitoring precatalyst O2 adapts* or dither valve duty cycle will help identify problem.

Check fuel supply while condition exists.

Check in-line fuel filter. Replace if dirty or plugged.

Check fuel pressure.

Ignition system malfunction

Component malfunction

Check for proper ignition voltage output using spark tester.

Check spark plugs.

•

Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits.

•

Repair or replace as necessary.

•

Check condition of distributor cap, rotor and spark plug wires (where applicable).

•

Check ignition timing.

Check vacuum lines for kinks or leaks.

Check alternator output voltage. Repair if less than

9 or more than 16 volts.

Exhaust backpressure

Check condition of exhaust system.

Check backpressure before catalyst. It should be less than 3.5 psig (24.13 kPa).

(

*

) Refer to Table 1 for description of gaseous O2 adapts.

Related MIL Faults:

Pre-catalyst O2 sensor errors / O2 control errors

Dither valve DC faults / EST faults / ETC faults




Engine Cranking but Will Not Start / Difficult to Start

Engine cranks OK, but does not start for a long time. Does eventually run, or may start but immediately dies.



Be sure driver is using correct method to start engine as explained in operator’s manual. Use “clear flood” mode during cranking by fully depressing the pedal and cranking the engine. If engine does not start, continue troubleshooting.


Plugged fuel line

Clogged fuel filter

Faulty vapor connection between the pressure regulator and the mixer

Fuel lock-off malfunction

Pressure regulator malfunction

Remove obstruction from the fuel line.

•

Using caution, disconnect the fuel line

(some natural gas may escape).

•

Clear obstruction with compressed air.

•

Re-connect fuel line.

•

Leak test.

Repair/replace as required.

See Chapter 3 Fuel Filter replacement.

Check connection

•

Verify no holes in hose.

•

Clamps must be tight.

•

Look for kinked, pinched and/or collapsed hose.

Repair/replace fuel lock-off.

See Chapter 3 Fuel Lock-off.

Test regulator operation and pressure.

See Chapter 5 Tests and Adjustments.

Incorrect air/fuel or ignition/spark control

See Chapter 7 Advanced Diagnostics.

No crankshaft position sensor signal

SECM / control system malfunction

Verify the crankshaft position signal is present


Check Coolant Temperature Sensor using the

Service Tool; compare coolant temperature with ambient temperature on cold engine.

If coolant temperature reading is 5° greater than or less than ambient air temperature on a cold engine, check resistance in coolant sensor circuit or sensor itself. Compare CTS resistance value to “Diagnostic Aids” chart at end of this section.

Verify that there is no code for ETC spring check fault.

Check for 0% APP during cranking.

Cycle key ON and OFF and listen for throttle check (movement) on key OFF.

Check for oil pressure switch faults.

Check for sensor “sticking” faults.

Check TPS for stuck binding or a high TPS voltage with the throttle closed.




PROBABLE CAUSE



Check fuel lock off: actuator should turn “ON” for

2 seconds when ignition is turned “ON”.


Check for contaminated fuel.

Check lock off fuses (visually inspect).

Check FTV system for proper operation.

CORRECTIVE ACTION

Check for proper ignition voltage output with spark tester.

Check spark plugs. Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Repair or replace as necessary.

Check for:

•

Moisture in distributor cap*

•

Bare or shorted wires

•

Worn distributor shaft/rotor*

•

Loose ignition coil ground

•

Pickup coil resistance and connections

(*)

Where present


ETC spring check / ETC faults / EST faults / TPS conflict

APP faults / Encoder error / MAP faults / Oil pressure faults

(continued on next page)

Engine Cranking but Will Not Start / Difficult to Start (cont’d.)





Lack of Power, Slow to Respond / Poor High Speed Performance / Hesitation During

Acceleration

Engine delivers less than expected power. Little or no increase in speed when accelerator pedal is pushed down part way. Momentary lack of response as the accelerator is pushed down. Can occur at all vehicle speeds. Usually most severe when first trying to make vehicle move, as from a stop. May cause engine to stall.



Drive vehicle; verify problem exists.

Remove air filter and check for dirt or other means of plugging. Replace if needed.

PROBABLE CAUSE




Check for restricted fuel filter.

Check fuel supply.


Check for clogged fuel filter and repair or replace as required. See Chapter 3 Fuel Filter replacement

Check for plugged fuel line and remove any obstruction from the fuel line:

•



•


•


Check for faulty vapor connection between pressure regulator and mixer:

•

Verify that there are no holes in hose.

•

Observe that clamps are tight.

•


Monitor pre-catalyst O2 with Service Tool.

Check for proper pressure regulator operation.

See Chapter 5 Test and Adjustments.

Check for proper air/fuel mixer operation.

Check spark advance for excessive retarded ignition timing. Use Service Tool.

Check secondary voltage using an oscilloscope or a spark tester to check for a weak coil.

Check spark plug condition.

Check poor spark plug primary and secondary wire condition.




Lack of Power, Slow to Respond / Poor High Speed Performance

Hesitation During Acceleration (cont’d.)

PROBABLE CAUSE

CORRECTIVE ACTION


Check SECM grounds for cleanliness and secure connection. See SECM wiring diagrams.

Check alternator output voltage. Repair if less than

9 volts or more than 16 volts.

Check for clogged air filter and clean or replace as required.

Check exhaust system for possible restriction.

Refer to Chart T-1 on later pages.

Inspect exhaust system for damaged or collapsed pipes.

•

Inspect muffler for heat distress or possible internal failure.

•

Check for possible plugged catalytic converter by comparing exhaust system backpressure on each side at engine.

Check backpressure by removing Precatalyst O2 sensor and measuring backpressure with a gauge.


Engine mechanical

See Engine Manufacturer’s Service Manual.

Check engine valve timing and compression

Check engine for correct or worn camshaft.


EST faults

ETC faults

ETC spring check

TPS faults

APP faults

Encoder error

Delayed Shutdown faults




Detonation / Spark Knock

A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with throttle opening (similar to the sound of hail striking a metal roof).





Cooling system malfunction


Exhaust system malfunction


To determine if the condition is caused by a rich or lean system, the vehicle should be driven at the speed of the complaint. Monitoring with the Service Tool will help identify problem.

Check for obvious overheating problems:

•

Low engine coolant

•

Loose water pump belt

•

Restricted air flow to radiator, or restricted water flow through radiator

•

Inoperative electric cooling fan

•

Correct coolant solution should be a mix of anti-freeze coolant (or equivalent) and water

•

High coolant temperature


Check spark module wiring.

Check exhaust backpressure.

Check for debris clogging the catalyst.

Check that pre-catalyst O2 sensor is functioning.

Engine mechanical

Check for excessive oil in the combustion chamber and/or blow by from excessive PCV flow.

Check combustion chambers for excessive carbon build up.

Check combustion chamber pressure by performing a compression test.

Check for incorrect basic engine parts such as cam, heads, pistons, etc.


EST faults

Encoder error

High coolant temperature faults



Backfire

Fuel ignites in intake manifold or in exhaust system, making loud popping noise.




Simulate condition by reviewing operation procedure practiced by vehicle operator.

PROBABLE CAUSE



Engine mechanical


Perform fuel system diagnosis check:

•

Check for fuel leaks

•

Check for MIL faults

•

Check for damaged components

Check proper ignition coil output voltage with spark tester.

Check spark plugs. Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Repair or replace as necessary.

Check spark plug wires for crossfire; also inspect distributor cap, spark plug wires and proper routing of plug wires.


Check compression: look for sticking or leaking valves.

Check intake and exhaust manifold for casting flash and gasket misalignment.

Refer to Engine Manufacturer’s Service Manual.


EST faults / ETC faults / Encoder error

Pre-catalyst O2 sensor faults

Dieseling, Run-on

Engine continues to run after key is turned “OFF,“ but runs very roughly. If engine runs smoothly, check ignition switch and adjustment.





Check for fuel leaks.

Ignition switching

Make sure power to system is shut off when key is in

OFF position.

Fuel lock off valve

Make sure lock off valve is closing properly.


Check spark advance at idle.


EST faults / ETC faults / Pre-catalyst O2 sensor faults




Rough, Unstable, Incorrect Idle, or Stalling

Engine cranks OK, but does not start for a long time. Does eventually run, or may start but immediately dies.



Check for vacuum leaks.

Check that SECM grounds are clean and tight. See SECM wiring diagram.

PROBABLE CAUSE



Monitor oxygen feedback to help identify the cause of the problem. If the system is running lean or if the system is running rich evaluate further i.e. dither valve duty cycle.

Check for incorrect minimum idle speed that may be caused by foreign material accumulation in the throttle bore, on the throttle valve, or on the throttle shaft.

The pre-catalyst oxygen (O2) sensor should respond quickly to different throttle positions. If it does not, then check the pre-catalyst O2 sensor for contamination. If the pre-catalyst O2 sensor is aged or contaminated, the SECM will not deliver correct amount of fuel, resulting in a drivability problem.


Check ignition system; wires, plugs, etc.

Natural gas pressure regulator malfunction


See Chapter 5 Tests and Adjustments

Air/fuel mixer malfunction Check mixer.


Engine mechanical

Check throttle for sticking or binding.

Check PCV valve for proper operation by placing finger over inlet hole in valve end several times. Valve should snap back. If not, replace valve.

Check alternator output voltage. Repair if less than 9 or more than 16 volts.

Perform a cylinder compression check.

See Engine Manufacturer’s Service Manual.





Rough, Unstable, Incorrect Idle, or Stalling (cont’d.)

PROBABLE CAUSE

Clogged fuel filter

Plugged fuel line

Fuel lock-off malfunction

Faulty vapor connection between the pressure regulator and the mixer

Vacuum leak


Repair/replace as required

See Chapter 3 Fuel Filter Replacement

Remove obstruction from the fuel line.

•



•


•


Repair/replace fuel lock-off.

See Chapter 3 Fuel Lock-Off.

Check connection.

•

Verify no holes in hose.

•

Clamps must be tight.

•


Check for vacuum leaks . . .

•

Between mixer and throttle body

•

Between throttle body and intake manifold

•

Between intake manifold and cylinder head


EST faults

ETC Sticking fault

Pre-catalyst adapts error




Cuts Out, Misses

Steady pulsation or jerking that follows engine speed, usually more pronounced as engine load increases, sometimes above 1500 rpm. The exhaust has a steady spitting sound at idle or low speed.



PROBABLE CAUSE




Engine mechanical


Check fuel system specifically for plugged fuel filter, low pressure.


Check lock off intermittent connection.

Check dither valve operation.

Check for spark on the suspected cylinder(s) using a shop oscilloscope or spark tester or equivalent. If no spark, check for intermittent operation or miss. If there is a spark, remove spark plug(s) in these cylinders and check for cracks, wear, improper gap, burned electrodes, heavy deposits.

Check spark plug wires by connecting ohmmeter to ends of each wire in question. If meter reads over

30,000 ohms, replace wire(s).

Visually inspect distributor cap, rotor, and wires for moisture, dust, cracks, burns, etc. Spray plug wires with fine water mist to check for shorts.

Check engine ground wire for looseness or corrosion.

Check for electromagnetic interference (EMI). A missing condition can be caused by EMI on the reference circuit. EMI can usually be detected by monitoring engine rpm with Service Tool. A sudden increase in rpm with little change in actual engine rpm indicates EMI is present. If problem exists, check routing of secondary wires and check distributor ground circuit.

Check intake and exhaust manifolds for casting flash or gasket leaks.

Perform compression check on questionable cylinders. If compression is low, repair as necessary.

Check base engine. Remove rocker covers and check for bent pushrods, worn rocker arms, broken valve springs, worn camshaft lobes, and valve timing.

Repair as necessary.


EST faults

ETC Sticking fault




Poor Fuel Economy / Excessive Fuel Consumption

Natural Gas Exhaust Smell

Fuel economy, as measured during normal operation, is noticeably lower than expected. Also, economy is noticeably lower than what it has been in the past. Natural gas fuel smell near vehicle sets off carbon monoxide sensors.



Verify operator complaint: identify operating conditions.

Check operator’s driving habits:

Are tires at correct pressure?

Are excessively heavy loads being carried?

Is acceleration too much, too often?

Check air cleaner element (filter) for being dirty or plugged.

Visually (physically) check vacuum hoses for splits, kinks, and proper connections.






Pressure regulator malfunction / fuel pressure too high

Check for faulty pressure regulator.

Check that dither valve duty cycle is < 15%.

Check for too high natural gas pressure at mixer

(> 1” positive pressure).

Monitor Pre-catalyst O2 sensor with Service Tool.

Check engine coolant level.

Check engine thermostat for faulty part (always open) or for wrong heat range.


Check for weak ignition and/or spark control.

Check spark plugs. Remove spark plugs and check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Repair or replace as necessary.

Check for exhaust system restriction or leaks.

Check induction system and crankcase for air leaks.

Check for clogged air filter; clean or replace as required.

Check FTV for housing cracks or obstructions; repair or replace as required.

Check for vacuum leak. Check system vacuum hoses from regulator to FTV and mixer. Repair or replace as required.

Air/fuel mixer malfunction Check mixer.

Engine mechanical


See Chapter 5 Tests and Adjustments.

Check compression.

Refer to Engine Manufacturer’s Service Manual.


Pre-catalyst O2 sensor faults / Low side driver / Dither valve duty cycle

EST faults / Fuel adapt faults / Low coolant temperature




High Idle Speed

Engine idles above the range of 750-1000 rpm.



PROBABLE CAUSE

Incorrect idle speed control

Throttle sticking

Foot pedal sticking or incorrect pedal signal

Engine mechanical


Check all hoses and gaskets for cracking, kinks, or leaks.

Verify that there are no vacuum leaks.

See Chapter 7 Advanced Diagnostics & Chapter 5

Tests and Adjustments

Replace throttle.

See Fault Code 461: ETC_Sticking

Check pedal return spring travel for binding.

Check APP function with Service Tool.

Verify smooth change of APP reading with pedal movement.


Check for vacuum hose leak.

Check for PCV malfunction.

Check for defective intake gasket.


ETC Sticking fault

Idle adapt out of range

MAP Sticking fault

MAP high value



Excessive Exhaust Emissions or Odors

Vehicle has high CO emissions.

NOTE: Excessive odors do not necessarily indicate excessive emissions.


Verify that no stored codes exist.

If emission test shows excessive CO and HC, check items that cause vehicle to run

rich.

If emission test shows excessive NOx, check items that cause vehicle to run lean or too hot.

PROBABLE CAUSE







If the Service Tool indicates a very high coolant temperature and the system is running lean:

•

Check engine coolant level.

•

Check engine thermostat for faulty part

(always open) or for wrong heat range.

•

Check fan operation

If the system is running rich, refer to “Diagnostic Aids” chart on the next page.

If the system is running lean refer to “Diagnostic Aids” chart on the next page.

Check for properly installed fuel system components.



Check spark plugs, plug wires, and ignition components.


Check for contamination for catalytic converter (look for the removal of fuel filler neck restrictor).

Check for carbon build-up. Remove carbon with quality engine cleaner. Follow instructions on label.

Check for plugged PCV valve.

Check for stuck or blocked PCV hose.

Check for fuel in the crankcase.


Low side driver

Fuel adapt faults

EST faults




Diagnostic Aids for Rich / Lean Operation

SERVICE TOOL

ITEM

Pre-catalyst O2 A/ D counts

Pre-catalyst O2 sensor switching between high and low

Trim valve duty cycle

RICH

Consistently > 250

Always high ADC

Malfunction codes

> 90%

• Pre-catalyst O2 sensor failed rich

• Pre-catalyst O2 sensor high

• Fuel adapts

Closed loop operation Stuck in open loop

LEAN

Consistently < 170

Always low ADC

< 10%

• Pre-catalyst O2 sensor failed lean

• Pre-catalyst O2 sensor low

• Fuel adapts

Stuck in open loop

RICH OPERATION

Gaseous fuel (Trim valve duty cycle>90%)

• Inspect hoses from AVV port (port on bottom of mixer) to trim valves and regulator for leaks or blockages, replace as necessary.

• Inspect in-line orifices for blockages (in wye), replace as necessary

• Check trim valves for proper operation, replace as necessary

• Check regulator out pressure, replace if out of spec

• Inspect fuel cone for damage, replace mixer assembly as necessary

LEAN OPERATION

Gaseous fuel (trim valve duty cycle<10%)

• Check for vacuum leaks, replace hoses, o-rings, and gaskets as necessary

• Check balance line for blockage, replace as necessary

• Check vapor hose for restrictions, replace as necessary

• Check trim valves for proper operation, replace as necessary

• Check regulator out pressure, replace if out of spec



Chart T-1

Restricted Exhaust System Check

Proper diagnosis for a restricted exhaust system is essential before replacement of any components. The following procedures may be used for diagnosis, depending upon engine or tool used.

CHECK AT PRE-CATALYST OXYGEN (O

2

) SENSOR

1. Carefully remove pre-catalyst oxygen (O

2

) sensor.

2. Install exhaust backpressure tester or equivalent in place of O

2

sensor using Snap-On P/N

EEVPV311A kit and YA8661 adapter or Mac tool. See Figure 26.

3. After completing test described below, be sure to coat threads of O

2

sensor with anti-seize compound prior to re-installation.

ILLUSTRATION NOTES

[1] Backpressure gage

[2] Pre-catalyst Oxygen (O

2

) sensor

[3] Exhaust manifold

Courtesy of GM 1991 Service Manual for Chevrolet Camaro © 1990

Figure 26 . Installing Exhaust Backpressure Tester

DIAGNOSIS:

1. With the engine idling at normal operating temperature, observe the exhaust system backpressure reading on the gage. Reading should not exceed 1.25 psig (8.61 kPa).

2. Increase engine speed to 2000 RPM and observe gage. Reading should not exceed 3 psig (20.68 kPa).

3. If the backpressure at either speed exceeds specification, a restricted exhaust system is indicated.

4. Inspect the entire exhaust system for a collapsed pipe, heat distress, or possible internal damage, split welds, or cracked pipe.

5. If there are no obvious reasons for the excessive backpressure, the catalytic converter is restricted and should be replaced using current recommended procedures.



Chapter 7.

Advanced Diagnostics

PG-08 systems are equipped with built-in fault diagnostics. Detected system faults can be displayed by the

Malfunction Indicator Lamp (MIL) as Diagnostic Fault Codes (DFC) or flash codes, and viewed in detail with the use of the Service Tool software. When the ignition key is turned on, the MIL will illuminate and remain on until the engine is started. Once the engine is started, the MIL lamp will go out unless one or more fault conditions are present. If a detected fault condition exists, the fault or faults will be stored in the memory of the small engine control module (SECM). Once an active fault occurs the MIL will illuminate and remain ON. This signals the operator that a fault has been detected by the SECM.

Reading Diagnostic Fault Codes

All PG-08 fault codes are three-digit codes. See MotoService Tool Handbook. Active and stored fault codes will be displayed on the Diagnostic Service Tool.

Displaying Fault Codes (DFC) from SECM Memory

See MotoService Tool Handbook. Active and stored fault codes will be displayed on the Diagnostic Service

Tool.

Clearing Fault (DFC) Codes

See MotoService Tool Handbook

CAUTION

Once the fault list is cleared it cannot be restored.

Fault Action Descriptions

Each fault detected by the SECM is stored in memory (FIFO) and has a specific action or result that takes place. Listed below are the descriptions of each fault action.

Engine Shutdown: The most severe action is an Engine Shutdown. The MIL will light and the engine will immediately shut down, stopping spark and closing the fuel lock-off solenoid valve.

Delayed Engine Shutdown: Some faults, such as low oil pressure, will cause the MIL to illuminate for 30 seconds and then shut down the engine.

Cut Fuel: Fuel flow will be turned off.

Cut Throttle: The throttle moves to its default position. The engine will run at idle but will not accelerate.

Turn on MIL: The MIL will light by an active low signal provided by the SECM, indicating a fault condition. May illuminate with no other action or may be combined with other actions, depending on which fault is active.

Soft Rev Limit / Medium Rev Limit / Hard Rev Limit: System will follow various sequences to bring engine speed back to acceptable levels.

Level4 Power Limit / Level3 Power Limit / Level2 Power Limit / Level1 Power Limit: The maximum engine power output will be limited to one of four possible levels. The engine power is calculated from measured engine parameters (e.g. MAP, rpm, fuel flow, etc).

Disable Gas O2 Control: In natural gas mode, closed loop correction of air fuel ratio based on the Pre-catalyst

O2 sensor is disabled.



Fault List Definitions

All the analog sensors in the PG-08 system have input sensor range faults. These are the coolant temperature sensor, fuel temperature sensor, throttle position sensors, pedal position sensors, manifold pressure sensor,

HEGO sensors, and intake air temperature sensor. Signals to these sensors are converted into digital counts by the SECM. A low/high range sensor fault is normally set when the converted digital counts reach the minimum of 0 or the maximum of 1024 (1024 = 5.0 Vdc with ~ 204 counts per volt).

Additionally, the SECM includes software to learn the actual range of the throttle position settings and throttle position sensors in order to take full advantage of the sensor range. Faults are set if the learned values are outside of the normal expected range of the sensor (e.g. APP1AdaptLoMin).

Table 1. Fault List Definitions

FAULT DESCRIPTION CODE

APP1AdaptHiMax

APP1AdaptHiMin

APP1AdaptLoMax

APP1AdaptLoMin

APP1RangeHigh

APP1RangeLow

APP2AdaptHiMax

Learned full pedal end of

APP1 sensor range higher than expected


APP1 sensor range lower than expected

Learned idle end of APP1 sensor range higher than expected

Learned idle end of APP1 sensor range lower than expected

APP1 sensor voltage out of range high, normally set if the

APP1 signal has shorted to power or the ground for the sensor has opened

APP1 sensor voltage out of range low, normally set if the

APP1 signal has shorted to ground, circuit has opened or sensor has failed


APP2 sensor range higher than expected

641

651

661

631

621

611

642



Table 1. Fault List Definitions (cont’d.)

FAULT

APP2AdaptHiMin

APP2AdaptLoMax

APP2AdaptLoMin

APP2RangeHigh

APP2RangeLow

APP_Sensors_Conflict

CamEdgesFault

CamSyncFault

CrankEdgesFault

CrankSyncFault

ECTOverTempFault

ECTRangeHigh

DESCRIPTION

Learned full pedal value of

APP

2

sensor range lower than expected

Learned idle value of APP

2 sensor range higher than expected


2 sensor range lower than expected

APP

2

sensor voltage out of range high, normally set if the

APP

2

signal has shorted to power or the ground for the sensor has opened

APP

2

sensor voltage out of range low, normally set if the

APP

2

signal has shorted to ground, circuit has opened or sensor has failed

APP position sensors do no not track well, intermittent connections to APP or defective pedal assembly

No CAM signal when engine is known to be rotating, broken

CAM sensor leads or defective

CAM sensor

Loss of synchronization on the

CAM sensor, normally due to noise on the signal or an intermittent connection on the

CAM sensor

No crankshaft signal when engine is known to be rotating, broken crankshaft sensor leads or defective crank sensor

Loss of synchronization on the crankshaft sensor, normally due to noise on the signal or an intermittent connection on the crankshaft sensor

Engine Coolant Temperature is High. The sensor has measured an excessive coolant temperature typically due to the engine overheating.

Engine Coolant Temperature

Sensor Input is High. Normally set if coolant sensor wire has been disconnected or circuit has opened to the SECM.

CODE

652

662

632

622

612

691

191

192

193

194

161

151




FAULT DESCRIPTION

ECTRangeLow

ECT_IR_Fault

EST1_Open

EST1_Short

ETCSpringTest

ETC_Open_Fault

ETC_Sticking

FuelSelectConflict

FuelTempRangeHigh

FuelTempRangeLow

GasFuelAdaptRangeHi

GasFuelAdaptRangeLo

GasO2FailedLean

Engine Coolant Temperature Sensor Input is

Low. Normally set if the coolant sensor wire has shorted to chassis ground or the sensor has failed.

Engine Coolant Temperature not changing as expected

EST1 output open, possibly open EST1 signal or defective spark module

EST1 output shorted high or low, EST1 signal shorted to ground or power or defective spark module

Electronic Throttle Control Spring Return Test has Failed. The SECM will perform a safety test of the throttle return spring following engine shutdown. If this spring has become weak the throttle will fail the test and set the fault.

NOTE: Throttle assembly is not a serviceable item and can only be repaired

by replacing the DV-EV throttle assembly.

Electronic Throttle Control Driver has failed.

Normally set if either of the ETC driver signals have opened or become disconnected, electronic throttle or SECM is defective.

Electronic Throttle Control is Sticking. This can occur if the throttle plate (butterfly valve) inside the throttle bore is sticking. The plate sticking can be due to some type of obstruction; a loose throttle plate or worn components shaft bearings.

NOTE: Throttle assembly is not a serviceable item and can only be repaired

by replacing the DV-EV throttle assembly.

Conflict in fuel select signals, normally set if one or both of the fuel select signals are shorted to ground

Fuel Temperature Sensor Input is High.

Normally set if the fuel temperature sensor wire has been disconnected or the circuit has opened to the SECM.

Fuel Temperature Sensor Input is Low.

Normally set if the fuel temperature sensor wire has shorted to chassis ground or the sensor has failed.

In natural gas mode, system had to adapt lean more than expected

In natural gas mode, system had to adapt rich more than expected

Pre-catalyst O

2

sensor indicates extended lean operation on natural gas

CODE

141

171

421

431

481

471

461

181

932

931

731

721

751



FAULT

GasO2FailedRich

GasO2NotActive

HardOverspeed



GasPostO2FailedRich

GasPostO2FailedLean

GasPostO2Inactive

HbridgeFault_ETC

DESCRIPTION

Pre-catalyst O

2

sensor indicates extended rich operation on natural gas

Pre-catalyst O

2

sensor inactive on natural gas, open O

2

sensor signal or heater leads, defective O

2 sensor, or defective FTVs

Post-catalyst O

2

sensor control on natural gas has reached rich limit and sensor still reads too lean. This could be caused by oxygen leak before or just after sensor, catalyst failure, sensor failure, or wiring/relay failure causing the sensor to not be properly heated. If any Pre-O

2 sensor faults are set, diagnose these first and after correcting these faults recheck if this fault sets.

Post-catalyst O

2

sensor control on natural gas has reached lean limit and sensor still reads too rich. This could be caused by catalyst failure, sensor failure, or wiring/relay failure causing the sensor to not be properly heated. If any Pre-O

2 sensor faults are set diagnose, these first and after correcting these faults recheck if this fault sets.

Post-catalyst O

2

sensor control on natural gas has sensed the O

2 sensor is not responding as expected.

If any Pre-O

2

sensor faults are set diagnose these first and after correcting these faults recheck if this fault sets. Possible causes for this fault are sensor disconnected, sensor heater failed, sensor element failed, heater relay, or SECM control of heater relay is disconnected or failed.

(Electronic Throttle Control Driver has Failed)

Indeterminate fault on Hbridge driver for Electronic Throttle Control.

Possibly either ETC+ or ETC- driver signals have been shorted to ground

Engine speed has exceeded the third level (3 of 3) of overspeed protection

CODE

771

741

772

752

742

491

571




FAULT

IATRangeHigh

IATRangeLow

IAT_IR_Fault

LSDFault_CrankDisable

LSDFault_Dither1

LSDFault_Dither2

LSDFault_LockOff

LSDFault_MIL

LowOilPressureFault

MAPRangeHigh

MAPRangeLow

MAPTimeRangeHigh

DESCRIPTION

Intake Air Temperature Sensor Input is High normally set if the IAT temperature sensor wire has been disconnected, the circuit has opened to the SECM, or a short to Vbatt has occurred.

Intake Air Temperature Sensor Input is Low normally set if the IAT temperature sensor wire has shorted to chassis ground or the sensor has failed.

Intake Air Temperature not changing as expected

Crank Disable Fault, signal has opened or shorted to ground or power or defective crank disable relay

Dither Valve 1 Fault, signal has opened or shorted to ground or power or defective dither 1 valve

Dither Valve 2 Fault, signal has opened or shorted to ground or power or defective dither 2 valve

Fuel lock off Valve Fault, signal has opened or shorted to ground or power or defective Fuel lock off valve

Malfunction Indicator Lamp Fault, signal has opened or shorted to ground or power or defective MIL lamp

Low engine oil pressure

Manifold Absolute Pressure Sensor

Input is High, normally set if the

TMAP pressure signal wire has become shorted to power, shorted to the IAT signal, the TMAP has failed or the SECM has failed.


Input is Low, normally set if the

TMAP pressure signal wire has been disconnected or shorted to ground or the circuit has opened to the SECM


Input is High, normally set if the

TMAP pressure signal wire has become shorted to power, shorted to the IAT signal, the TMAP has failed or the SECM has failed.

CODE

381

371

391

715

711

712

717

718

521

342

332

341




FAULT DESCRIPTION

MAPTimeRangeLow

MAP_IR_HI

MAP_IR_LO

MAP_STICKING

MediumOverspeed

O2RangeHigh

O2RangeLow

O2_PostCatRangeHigh

O2_PostCatRangeLow

SensVoltRangeHigh

SensVoltRangeLow

ServiceFault1

ServiceFault2

ServiceFault3

ServiceFault4

ServiceFault5

SoftOverspeed

SysVoltRangeHigh

SysVoltRangeLow

Manifold Absolute Pressure Sensor Input is Low, normally set if the TMAP pressure signal wire has been disconnected or shorted to ground or the circuit has opened to the SECM

MAP sensor indicates higher pressure than expected

MAP sensor indicates lower pressure than expected

MAP sensor not changing as expected

Engine speed has exceeded the second level (2 of

3) of overspeed protection

Pre-catalyst O

2

sensor voltage out of range high, sensor signal shorted to power

Pre-catalyst O

2

sensor voltage out of range low, sensor signal shorted to ground

Post-catalyst O

2

sensor voltage out of range high, sensor signal shorted to voltage source (5V or battery)

Post-catalyst O

2


Sensor reference voltage XDRP too high

Sensor reference voltage XDRP too low

Service Interval 1 has been reached



Service Interval 4 has been reached—time to replace HEGO sensors


Engine speed has exceeded first level

(1 of 3) of overspeed protection

System voltage too high

System voltage too low

CODE

331

351

352

353

572

921

911

922

912

561

551

991

992

993

994

995

573

541

531




FAULT

TPS1AdaptHiMax

TPS1AdaptHiMin

TPS1AdaptLoMax

TPS1AdaptLoMin

TPS1RangeHigh

TPS1RangeLow

TPS2AdaptHiMax

TPS2AdaptHiMin

TPS2AdaptLoMax

TPS2AdaptLoMin

TPS2RangeHigh

TPS2RangeLow

TPS_Sensors_Conflict

DESCRIPTION

Learned WOT value of TPS

1

sensor range higher than expected


1


Learned closed throttle value of TPS

1



1


TPS

1

sensor voltage out of range high, normally set if the TPS

1

signal has shorted to power or ground for the sensor has opened

TPS

1

sensor voltage out of range low, normally set if TPS

1



2



2



2



2


TPS

2

sensor voltage out of range high, normally set if the TPS

2

signal has shorted to power or ground for the sensor has opened

TPS

2

sensor voltage out of range low, normally set if TPS

2


TPS sensors differ by more than expected amount.

NOTE: The TPS is not a serviceable item and can only be repaired by replacing the

DV-EV throttle assembly

CODE

251

271

281

241

231

221

252

272

282

242

232

222

291



Table 2. Diagnostic Fault Codes (Flash Codes)

DFC

12

141

151

161

171

181

191

PROBABLE FAULT

FAULT

ACTION

*


FIRST CHECK

NONE

Signifies the end of one pass through the fault list

NONE

None, used as end of the fault list identification

ECTRangeLow

Coolant Sensor failure or shorted to

GND

ECTRangeHigh

Coolant sensor disconnected or open circuit

ECTOverTempFault

Engine coolant temperature is high.

The sensor has measured an excessive coolant temperature typically due to the engine overheating.

TurnOnMil

(1) TurnOnMil

(2) DelayedEngine

Shutdown

(3)

CheckEngineLight

(1) TurnOnMil

(2) DelayedEngine

Shutdown

(3)

CheckEngineLight

Check ECT sensor connector and wiring for a short to GND

SECM (Signal) Pin B15 To ECT

Pin A

SECM (Sensor GND) Pin B1 to

ECT Pin B

SECM (System GND) Pin A16,

B17

Check if ECT sensor connector is disconnected or for an open

ECT circuit

SECM (Signal) Pin B15 to ECT

Pin A


ECT Pin B

Check coolant system for radiator blockage, proper coolant level and for leaks in the system.

Possible ECT short to GND, check ECT signal wiring

SECM (Signal) Pin B15 to ECT

Pin A


ECT Pin B

SECM (System GND) Pin A16,

B17

Check regulator for coolant leaks

ECT_IR_Fault

Engine coolant temperature not changing as expected

FuelSelectConflict

Conflict in fuel select signals, normally set if both of the fuel select signals are shorted to ground

CamEdgesFault

No CAM signal when engine is known to be rotating, broken crankshaft sensor leads or defective

CAM sensor

NONE

TurnOnMil

NONE

Check for coolant system problems, e.g. defective or stuck thermostat

Check fuel select switch connection for a short to GND

SECM (SIGNAL) Pin A12

SECM (SIGNAL) Pin A15

SECM (Sensor GND) Pin B1

Check CAM sensor connections at distributor

SECM (SIGNAL) Pin B10 to distributor connector Pin B

SECM (Sensor GND) Pin B1 to distributor connector Pin A

SECM 5V (PWR) to distributor connector Pin C

Check for defective CAM sensor in distributor housing.

(*

)

Fault actions shown are default values specified by the OEM.



DFC

Table 2. Diagnostic Fault Codes (Flash Codes) cont’d.

PROBABLE FAULT

FAULT

ACTION

*


FIRST CHECK

Check CAM sensor connections at distributor

192

CamSyncFault

Loss of synchronization on the CAM sensor, normally due to noise on the signal or an intermittent connection on the

CAM sensor

NONE

SECM (SIGNAL) Pin B10 to distributor connector Pin B

SECM (Sensor GND) Pin B1 to distributor connector Pin A

SECM 5V (PWR) to distributor connector Pin C

Check for defective CAM sensor in distributor housing

193

194

221

222

CrankEdgesFault

No crankshaft signal when engine is known to be rotating, broken crankshaft sensor leads or defective crank sensor

CrankSyncFault

Loss of synchronization on the crankshaft sensor, normally due to noise on the signal or an intermittent connection on the crankshaft sensor

TPS1RangeLow

TPS

1


TPS

1


TPS2RangeLow

TPS

2


TPS

2


NONE

NONE

TurnOnMil

TurnOnMil

Check Crankshaft sensor connections

SECM (SIGNAL) Pin B5 to Crank sensor Pin C

SECM (Sensor GND) PIN B1 to

Crank sensor Pin B

SECM 5V (PWR) to Crank sensor Pin A

Check for defective Crank sensor

Check Crankshaft sensor connections

SECM (SIGNAL) Pin B5 to Crank sensor Pin C


Crank sensor Pin B

SECM 5V (PWR) to Crank sensor

Pin A

Check for defective Crank sensor

Check throttle connector connection and TPS

1

sensor for an open circuit or short to GND

SECM Pin B23 (signal) to ETC

Pin 6

SECM Pin B1 (sensor GND) to

ETC Pin 2

SECM (system GND) Pin A16,

B17

Check throttle connector connection and TPS

2

sensor for an open circuit or short to GND

SECM Pin B4 (signal) to ETC Pin

5


ETC Pin 2

SECM (system GND) Pin A16,

B17

(*

)




DFC


FAULT

PROBABLE FAULT


ACTION

*

FIRST CHECK

TPS1RangeHigh

231

232

TPS

1


TPS

1


TPS2RangeHigh

TPS

2


TPS

2


TurnOnMil

TurnOnMil

Check throttle connector and TPS

1 sensor wiring for a shorted circuit

SECM Pin B23 (signal) to ETC Pin 6


ETC Pin 2

Check throttle connector and TPS

1 sensor wiring for a shorted circuit

SECM Pin B4 (signal) to ETC Pin 5

SECM pin B1 (sensor GND) to

ETC Pin 2

241

242

TPS1AdaptLoMin


1


TPS2AdaptLoMin


2


NONE

NONE

Check the throttle connector and pins for corrosion.

To check the TPS disconnect the throttle connector and measure the resistance from:

TPS Pin 2 (GND) to

Pin 6 (TPS

1

SIGNAL) (0.7

Ω ± 30%)

TPS Pin 3 (PWR) to

Pin 6 (TPS

1

SIGNAL) (1.4

Ω ± 30%)

Check the throttle connector and pins for corrosion.

To check the TPS disconnect the throttle connector and measure the resistance from:

TPS Pin 2 (GND) to Pin 5 (TPS

2

SIGNAL) (1.3K

Ω ± 30%)

TPS PIN 3 (PWR) to PIN 5 (TPS

2

SIGNAL) (0.6K

Ω ± 30%)

251

252

TPS1AdaptHiMax

Learned WOT value of

TPS

1


TPS2AdaptHiMax


TPS

2


NONE

NONE

N/A

N/A

271

TPS1AdaptHiMin


TPS

1


NONE

272

TPS2AdaptHiMin


TPS

2


NONE

(

*

)


N/A

N/A



DFC


PROBABLE FAULT

FAULT

ACTION

*


FIRST CHECK

281

282

291

TPS1AdaptLoMax


1


TPS2AdaptLoMax


2


TPS_Sensors_Conflict

TPS sensors differ by more than expected amount

NOTE: The TPS is not

a serviceable item and can only be repaired by replacing the DV-EV

throttle assembly.

NONE

NONE

(1)

TurnOnMil

(2) Engine

Shutdown

N/A

N/A

Perform checks for DFCs 241

& 242

331

MAPTimeRangeLow

Manifold Absolute

Pressure sensor input is low, normally set if the

TMAP pressure signal wire has been disconnected or shorted to ground or the circuit has opened to the

SECM

NONE

Check TMAP connector and MAP signal wiring for an open circuit

TMAP Pin 4 to SECM Pin B18

(signal)


(sensor GND)


(PWR)

Check the MAP sensor by disconnecting the TMAP connector and measuring at the sensor:

TMAP Pin 1(GND) to Pin 4

(pressure signal kPa) (2.4k

Ω -

8.2k

Ω)

TMAP Pin 3 (PWR) to Pin 4


Ω -

8.2k

Ω)

(

*

)




DFC


PROBABLE FAULT

FAULT

ACTION

*


FIRST CHECK

332

341

342

MAPRangeLow

Manifold Absolute

Pressure sensor input is low, normally set if the

TMAP pressure signal wire has been disconnected or shorted to ground or the circuit has opened to the

SECM

MAPTimeRangeHigh

Manifold Absolute

Pressure Sensor Input is

High, normally set if the

TMAP pressure signal wire has become shorted to power, shorted to the

IAT signal, the TMAP has failed or the SECM has failed.

MAPRangeHigh

Manifold Absolute

Pressure Sensor Input is

High, normally set if the

TMAP pressure signal wire has become shorted to power, shorted to the

IAT signal, the TMAP has failed or the SECM has failed

(1)

TurnOnMil

(2)

CutThrottle

NONE

(1)

TurnOnMil

(2)

CutThrottle

Check TMAP connector and MAP signal wiring for an open circuit


(signal)


(sensor GND)


(PWR)




Ω -

8.2k

Ω)

TMAP Pin 3 (power) to Pin 4


Ω -

8.2k

Ω)

Check TMAP connector and MAP signal wiring for a shorted circuit


(signal)


(sensor GND)


(PWR)




Ω -

8.2k

Ω)



Ω -

8.2k

Ω)

Check TMAP connector and MAP signal wiring for a shorted circuit


(signal)


(sensor GND)


(PWR)




Ω -

8.2k

Ω)



Ω -

8.2k

Ω)

(

*

)




DFC


PROBABLE FAULT

FAULT

ACTION

*

CORRECTIVE ACTION,

FIRST CHECK

351

352

353

MAP_IR_HI

MAP sensor indicates higher pressure than expected

MAP_IR_LO

MAP sensor indicates lower pressure than expected

MAP_STICKING

MAP sensor not changing as expected

NONE

Check for vacuum leaks. Check that

TMAP sensor is mounted properly.

Possible defective TMAP sensor.

NONE Possible defective TMAP sensor.

NONE

371

381

391

421

IATRangeLow

Intake Air

Temperature Sensor

Input is Low normally set if the IAT temperature sensor wire has shorted to chassis ground or the sensor has failed.

IATRangeHigh

Intake Air

Temperature Sensor

Input is High normally set if the IAT temperature sensor wire has been disconnected or the circuit has opened to the SECM.

IAT_IR_Fault

Intake Air

Temperature not changing as expected

EST1_Open

EST1 output open, possibly open EST1 signal or defective spark module

TurnOnMil

TurnOnMil

NONE

TurnOnMil

Check that TMAP sensor is mounted properly. Possible defective TMAP sensor.

Check TMAP connector and IAT signal wiring for a shorted circuit


(signal)


(sensor GND)

To check the IAT sensor of the TMAP disconnect the TMAP connector and measure the IAT resistance

Resistance is approx 2400 ohms at room temperature.

Check TMAP connector and IAT signal wiring for a shorted circuit


(signal)


(sensor GND)

To check the IAT sensor of the TMAP disconnect the TMAP connector and measure the IAT resistance

Resistance is approx 2400 ohms at room temperature.

Check connections to TMAP sensor.

Check that TMAP sensor is properly mounted to manifold.

Check ignition module wiring and connector for open circuit

SECM Pin A9 (EST1) to ignition module Pin B.

Verify GND on ignition module Pin C

Verify +12 Vdc on ignition module

Pin A

Refer to application manual for specific engine details.

(

*

)




DFC


FAULT

PROBABLE FAULT


ACTION

*

FIRST CHECK

Check ignition module wiring and connector for shorts

431

EST1_Short

EST1 output shorted high or low, EST1 signal shorted to ground or power or defective spark module

TurnOnMil

SECM Pin A9 (EST1) to ignition module Pin B

Verify GND on ignition module Pin C

Verify +12 Vdc on ignition module

Pin A

Refer to application manual for specific engine details.

Check for debris or obstructions inside the throttle body

* Check throttle-plate shaft for bearing wear

461

ETC_Sticking

Electronic Throttle

Control is sticking. This can occur if the throttle plate (butterfly valve) inside the throttle bore is sticking. The plate sticking can be due to some type of obstruction, a loose throttle plate, or worn components shaft bearings.

NOTE: The throttle

assembly is not a serviceable item and can only be repaired by replacing the DV-

EV throttle assembly.

(1)

TurnOnMil

(2)

EngineShut down

(3)

CutThrottle

Check the ETC driver wiring for an open circuit

SECM Pin A17 to ETC + Pin 1

SECM Pin A18 to ETC - Pin 4

Check the ETC internal motor drive by disconnecting the throttle connector and measuring the motor drive resistance at the throttle

ETC Pin 1 (+DRIVER) to

Pin 4 (-DRIVER) ~3.0-4.0

Ω

Check the ETC driver wiring for an open circuit

471

ETC_Open_Fault

Electronic Throttle

Control Driver has failed, normally set if either of the ETC driver signals have opened or become disconnected, electronic throttle or

SECM is defective.

NONE





Pin 4 (-DRIVER) ~3.0-4.0

Ω

Check ETC driver wiring for a shorted circuit

491

HbridgeFault_ETC

Electronic Throttle

Control Driver has failed. Indeterminate fault on Hbridge driver for electronic throttle control. Possibly either

ETC+ or ETC- driver signals have been shorted to ground

TurnOnMil





Pin 4 (-DRIVER) ~3.0-4.0

Ω

(

*

)




DFC

521


FAULT

PROBABLE FAULT


ACTION

*

FIRST CHECK

Check engine oil level

LowOilPressureFault

Low engine oil pressure

(1) TurnOnMil

(2) DelayedEngine

Shutdown

(3) CheckEngine

Light

Check electrical connection to the oil pressure switch

SECM Pin B9 to Oil Pressure

Switch

531

541

SysVoltRangeLow

System voltage too low

SysVoltRangeHigh

System voltage too high

TurnOnMil

TurnOnMil

Check battery voltage

* Perform maintenance check on electrical connections to the battery and chassis ground

* Check battery voltage during starting and when the engine is running to verify charging system and alternator function

* Measure battery power at

SECM with a multimeter

(with key on)

SECM Pin A23 (DRVP) to

SECM Pin A16 (DRVG)


SECM Pin B17 (DRVG)

Check battery and charging system voltage

* Check battery voltage during starting and when the engine is running

* Check voltage regulator, alternator, and charging system

* Check battery and wiring for overheating and damage

* Measure battery power at


(with key on)


SECM Pin A16 (DRVG)


SECM Pin B17 (DRVG)

(

*

)




DFC


PROBABLE FAULT

FAULT

ACTION

*


FIRST CHECK

551

SensVoltRangeLow

Sensor reference voltage XDRP too low

(1) TurnOnMil

(2) EngineShutdown

Measure transducer power at the

TMAP connector with a multimeter

TMAP Pin 3 (PWR) to TMAP Pin 1

(sensor GND)

Verify transducer power at the


SECM Pin B24 (PWR) to SECM

Pin B1 (sensor GND)

Verify transducer power at ETC with a multimeter

ETC Pin 3 (PWR) to ETC Pin 2

(sensor GND)

Verify transducer power to the foot pedal with a multimeter.

561

571

572

573

SensVoltRangeHigh

Sensor reference voltage XDRP too high

HardOverspeed

Engine speed has exceeded the third level (3 of 3) of overspeed protection

MediumOverspeed

Engine speed has exceeded the second level (2 of 3) of overspeed protection

SoftOverspeed

Engine speed has exceeded the first level (1 of 3) of overspeed protection

(1) TurnOnMil

(2) EngineShutdown

(1) TurnOnMil

(2) HardRevLimit

(1) TurnOnMil

(2) MediumRevLimit

(1) TurnOnMil

(2) SoftRevLimit

Measure transducer power at the

TMAP connector with a multimeter

TMAP Pin 3 (PWR) to TMAP Pin 1

(sensor GND)

Verify transducer power at the


SECM Pin B24 (PWR) to SECM

Pin B1 (sensor GND)

Verify transducer power at ETC with a multimeter

ETC Pin 3 (PWR) to ETC Pin 2

(sensor GND)

Verify transducer power to the foot pedal with a multimeter.

Usually associated with additional

ETC faults

* Check for ETC Sticking or other ETC faults

Verify if the lift truck was motored down a steep grade


ETC faults


Verify if the vehicle was motored down a steep grade


ETC faults


Verify if the vehicle was motored down a steep grade

611

APP1RangeLow

APP

1


APP

1


(1) TurnOnMil

(2) CheckEngineLight

Check foot pedal connector

* Check APP

1

signal at SECM

PIN B7

(

*

)




DFC


CORRECTIVE

FAULT

PROBABLE FAULT

ACTION

ACTION

*

FIRST CHECK

612

621

622

APP2RangeLow

APP

2


APP

2


APP1RangeHigh

APP

1


APP

1


APP2RangeHigh

APP

2


APP

2


TurnOnMil

(1) TurnOnMil

(2) CheckEngine Light

TurnOnMil


* Check APP

2 signal at SECM

PIN B16


* Check APP

1 signal at SECM

PIN B7


* Check APP

2 signal at SECM

PIN B16

Check APP connector and pins for corrosion

631

APP1AdaptLoMin



NONE

* Cycle the pedal several times and check APP

1 signal at SECM

Pin B7

632

APP2AdaptLoMin



NONE



2 signal at SECM

Pin B16

641

642

651

652

661

662

APP1AdaptHiMax


APP

1


APP2AdaptHiMax


APP

2


APP1AdaptHiMin


APP

1


APP2AdaptHiMin


APP

2


APP1AdaptLoMax



APP2AdaptLoMax



NONE

NONE

NONE

NONE

NONE

NONE

N/A

N/A

N/A

N/A

N/A

N/A

(

*

)




DFC


PROBABLE FAULT

FAULT

ACTION

*


FIRST CHECK

691

711

712

APP_Sensors_Conflict

APP position sensors do no not track well, intermittent connections to APP or defective pedal assembly

LSDFault_Dither1

Dither Valve 1 Fault, signal has opened or shorted to ground or power or defective dither

1 valve

LSDFault_Dither2

Dither Valve 2 Fault, signal has opened or shorted to ground or power or defective dither

2 valve

1) TurnOnMil

(2) Level1PowerLimit

TurnOnMil

TurnOnMil



1

signal at

SECM Pin B7


2

signal at

SECM Pin B16

Check FTV

1

for an open wire or FTV connector being disconnected

FTV

1

Pin 1 (signal) to

SECM Pin A1

FTV

1

Pin 2 (power) to

SECM (DRVP) Pin A23

Check FTV

1

for an open coil by disconnecting the

FTV connector and measuring the resistance

(~26

Ω ± 2Ω )

Check FTV

2

for an open wire or FTV connector being disconnected or signal shorted to GND

FTV

2

Pin 1 (signal) to

SECM Pin A2

FTV

2

Pin 2 (power) to

SECM (DRVP) Pin A23

Check FTV

2

for an open coil by disconnecting the

FTV connector and measuring the resistance

(~26

Ω ± 2Ω )

715

LSDFault_CrankDisable

Crank Disable Fault, signal has opened or shorted to ground or power or defective crank disable relay

NONE

N/A

(

*

)




DFC


PROBABLE FAULT

FAULT

ACTION

*


FIRST CHECK

Check fuel lock off valve for an open wire or connector being disconnected or signal shorted to GND

717

LSDFault_LockOff

Fuel lock off Valve Fault, signal has opened or shorted to ground or power or defective Fuel lock off valve

TurnOnMil

Lockoff Pin B (signal) to

SECM Pin A11 Lockoff Pin A

(power) to SECM (DRVP) Pin

A23

Check CSV for an open coil by disconnecting the CSV connector and measuring the resistance (~26

Ω ± 3Ω)

718

LSDFault_MIL

Malfunction Indicator Lamp

Fault, signal has opened or shorted to ground or power or defective MIL lamp

NONE

Check MIL lamp for an open wire or short to GND.

721

GasFuelAdaptRangeLo

In natural gas mode, system had to adapt rich more than expected

TurnOnMil


Check fuel trim valves, e.g. leaking valve or hose

Check for missing orifice(s).

731

GasFuelAdaptRangeHi

In natural gas mode, system had to adapt lean more than expected

TurnOnMil

Check fuel trim valves, e.g. plugged valve or hose.

Check for plugged orifice(s).

741

GasO2NotActive

Pre-catalyst O

2

sensor inactive on natural gas, open

O

2


2

sensor

(1) TurnOnMil

(2) DisableGas

O2Ctrl

Check that Pre-catalyst O

2 sensor connections are OK.

O

2

(signal) Pin B to SECM

Pin B13

O

2

Pin C (GND) to SECM

(DRVG GND) Pins A16, B17

O

2

Pin 1 (power) to SECM

(DRVP + 12V) Pin A23

Verify O

2

sensor heater circuit is operating by measuring heater resistance

(2.1

Ω ± 0.4Ω)

O

2

Pin C (GND) to Pin D

(power)

(

*

)





DFC

742

751

752

771

PROBABLE FAULT

GasPostO2NotActive

Post-catalyst O

2

sensor inactive on natural gas, open

O

2


2

sensor.

GasO2FailedLean

Pre-catalyst O

2


GasPostO2FailedLean

Post-catalyst O

2


GasO2FailedRich

Pre-catalyst O

2


FAULT

ACTION

*

(1) TurnOnMil

(2) DisableGasPost

O2Ctrl

(1) TurnOnMil

(2) DisableGas

O2Ctrl

(1) TurnOnMil

(2) DisableGasPost

O2Ctrl

(1) TurnOnMil

(2) DisableGas

O2Ctrl


FIRST CHECK

Check that Post-catalyst O

2 sensor connections are OK.

O

2

(signal) Pin B to SECM Pin

B19

O

2

Pin C (GND) to SECM

(DRVG GND) Pins A16, B17

O

2

Pin D (power) to Post O

2

Heater Relay. Relay pin 87. This relay only turns on after engine has been running for some time and SECM has calculated that water condensation in exhaust has been removed by exhaust heat. Post O

2

Heater Relay has

SECM (DRVP + 12V) applied to the relay coil power. The relay coil ground is controlled by

SECM Pin A20 to activate the relay to flow current through the post O

2

heater.

Verify O

2

sensor heater circuit is operating by measuring heater resistance (2.1

Ω ± 0.4Ω)

O

2

Pin C (GND) to Pin D

(power)


Check fuel trim valves, e.g. leaking valve or hose.

Check for missing orifice(s).

Correct other faults that may contribute to 752 (e.g. faults pertaining to fuel trim valves,

Pre-Cat O

2

, Post Cat O

2 sensor)

Check for vacuum leaks

Check for leaks in exhaust, catalytic converter, HEGO sensors; repair leaks.

Check all sensor connections

(see fault 742 corrective actions).

Check fuel trim valves, e.g. plugged valve or hose.

Check for plugged orifice(s).

(

*

)





DFC

772

911

912

921

922

PROBABLE FAULT

GasPostO2FailedRich

Pre-catalyst O

2


O2RangeLow

Pre-catalyst O

2


O2_PostCatRangeLow

Post-catalyst O

2


O2RangeHigh

Pre-catalyst O2 sensor voltage out of range high, sensor signal shorted to power

O2_PostCatRangeHigh

Post-catalyst O

2


FAULT

ACTION

*

(1) TurnOnMil

(2) DisableGasPost

O2Ctrl

(1) TurnOnMil

(2)

DisableGasO2Ctrl

(1) TurnOnMil

(2) Disable NG

Post-catalyst O2Ctrl

(1) TurnOnMil

(2) DisableGas

O2Ctrl

(1) TurnOnMil

(2) Disable NG

Post-catalyst O2Ctrl


FIRST CHECK

Correct other faults that may contribute to 772 (e.g. faults pertaining to FTVs, Pre-Cat

O

2

, Post Cat O

2

sensor)

Look for leaks in exhaust, catalytic converter, HEGO sensors; repair leaks.

Check all sensor connections (see fault 742 corrective actions).

Check if O

2

sensor installed before the catalyst is shorted to GND or sensor GND.

O

2


Pin B13

SECM (DRVG GND) Pins

A16, B17

SECM (sensor GND) Pin

B1

Check if O

2

installed after the catalyst sensor is shorted to GND or sensor

GND.

O

2


Pin B19

Possible sources: SECM

(DRVG GND) Pins A16,

B17 and SECM (sensor

GND) Pin B1

Check if O

2

sensor installed before catalyst is shorted to +5Vdc or battery.

O

2


Pin B13

SECM (PWR) Pin B24

SECM (power) Pin A23

Check if O

2

sensor installed after catalyst is shorted to +5Vdc or battery.

O

2


Pin B19

Possible voltage sources:

SECM (PWR) Pin B24 and

SECM (power) Pin A23

(

*

)





DFC

PROBABLE FAULT

FAULT

ACTION

*

931

932

991

992

993

994

995

FuelTempRangeLow

Fuel Temperature

Sensor Input is Low, normally set if the fuel temperature sensor wire has shorted to chassis ground or the sensor has failed.

FuelTempRangeHigh

Fuel Temperature

Sensor Input is High normally set if the fuel temperature sensor wire has been disconnected or the circuit has opened to the SECM.

ServiceFault1


ServiceFault2


ServiceFault3


ServiceFault4

Service Interval 4 has been reached—replace

HEGO sensors

ServiceFault5


TurnOnMil

TurnOnMil

NONE

NONE

NONE

TurnOnMil

TurnOnMil

(

*

)



FIRST CHECK

Check fuel temp sensor connector and wiring for a short to GND

SECM (signal) Pin B14 to FTS

Pin 1

SECM (sensor GND) Pin B1 to

FTS Pin 2

SECM (GND) Pin A16, B17

Check if fuel temp sensor connector is disconnected or for an open FTS circuit

SECM (signal) Pin B14 to FTS

Pin 1

SECM (sensor GND) Pin B1 to

FTS Pin 2

Perform service procedure related to Service Interval 1

(determined by OEM)


(determined by OEM)


(determined by OEM)

Replace Pre-catalyst HEGO sensor

Replace Post-catalyst HEGO sensor


(determined by OEM)



Chapter 8.

Parts Description

Fuel System Components

The chart below lists the PG-08 components required for an engine operating on natural gas fuel.

DESCRIPTION

Engine Control Module (SECM 48-pin)

QTY

1

Crankshaft Position Sensor

TMAP Sensor

Oxygen Sensors

Coolant Sensor

Engine Oil Pressure Switch

Fuel Trim Valves

Ignition Coils

Fuel Lock Off Solenoid

Maxitrol R600S Regulator

1

1

2

1

1

2

1

1

1

CA225 Mixer

Throttle-DV-E5 40mm

Throttle to Mixer Hose Adapter

1

1

1

Throttle Hose

Hose Clamps

Wye Fitting

Wye Orifice

1

2

1

2



CA225 Mixer

Refer to Figure 27 exploded view on facing page.

Parts List CA225 Mixer

REF

NO.

DESCRIPTION

1

Hex Head Screw, 1/4-20 x 1

2

3

4


Split Lockwasher, 1/4”

Fillister Head Screws, SEMS #10-24 UNC x 5/8

Mixer Cover

5

6

7

8

9

10

Air Valve Spring

Diaphragm, Fluorosilicone

Air Valve Ring

Mixer Body

Gasket, Throttle Body to Mixer

Fillister Head Screws, SEMS #12-24 x 5/8

QTY

1

1

1

1

5

1

1

1

1

4



Exploded View CA225 Mixer

Buck’s Engines

Figure 27. CA225 Mixer Exploded View

46


Maxitrol R600S Regulator

This R600S regulator is supplied from an outside vendor as a complete assembly. It has no servicable parts. If it tests defective, replace the entire regulator with the specified replacement assembly. The Maxitrol regulator is specifically engineered for the PG-08 system and cannot be replaced by a standard Maxtirol R600S regulator.

NOTE

The PG-08 system will malfunction if the incorrect regulator is substituted in the system. Please contact

Buck’s Engines’ component supplier for the correct replacement part.

Swing Radius 4.32” (109.7mm)

Dimension A 5.68” (144.3mm)

Dimension B 3.88” (98.3mm)

Dimension C 4.03” (102.4mm)

Dimension D 1.46” (37.1mm)



Appendix

Abbreviations

ACFM

Actual cubic feet per minute at the specified suction conditions

AFR Air fuel ratio

BHP Brake horsepower

BTU British Thermal Unit

Bi-Fuel Able to operate on either of two fuels

CTS Coolant temperature sensor

CNG Compressed natural gas

Dual Fuel

Able to run simultaneously on two fuels, e.g. diesel and natural gas. Often this term is incorrectly used to describe bi-fuel operation.

Spark-ignited engines are typically bi-fuel while compression ignition engines are dual-fuel.

ECM Engine control module

FPP Foot pedal position

FPV Fuel primer valve

FTV Fuel trim valve

GPM Gallons per minute of flow

HEGO Heated exhaust gas oxygen (sensor)

LAT Limited-angle torque motor

MAP Manifold absolute pressure

MAT Manifold air temperature

MIL Malfunction indicator lamp

MOR

Manufacturer of record for emissions certification on the engine

NG Natural gas

NSPS

New Source Performance Standards effective in 2008 for stationary spark-ignited engines.

OEM Original equipment manufacturer

PHI

Relative fuel-air ratio or percent of stoichiometric fuel (actual fuel-air ratio / stoichiometric fuel-air ratio)

RPM Revolutions per minute

SECM Small engine control module

TMAP Temperature and manifold absolute pressure

TPS Throttle position sensor

VDC Voltage of direct current type

VE Compressed natural gas

WOT Wide open throttle


Certified Engine

Troubleshooting

Types of Fuel Systems

•

3.0L, 4.3L, and 5.7L Use a dual fuel trim valve (dither valve) feedback fuel system

•

8.1L Uses a Woodward L-series trim valve feedback system

Duel Fuel Trim Components

•

Maxitrol 600s regulator

•

Fuel trim valves

•

Throttle Body

•

225 mixer

•

Vacuum wye

Maxitrol 600s regulator

Inlet fuel pressure 8 to 12 inH2O

Outlet fuel pressure

3.5 inH2O

Regulator pressure is controlled by vacuum introduced to a tee screwed into the top.

This is not field adjustable

Fuel trim valves

These control the amount of vacuum being supplied to the regulator. If you hold when the engine is running you would feel it clicking rapidly. This is providing a vacuum bias to the Maxitrol regulator

Throttle

Body

The throttle body provides control of engine speed

2 verities of Woodward 225 mixers

The Non-Adjustable

It will have either a locked power valve or no power valve at all.

The adjustable

It will have a functioning power valve and idle adjusting screw

Vacuum Wyes

The Black wye will free flow

The Blue wye will have a fixed orifice in it

L-series trim valve fuel control primary components

•

•

L-Series trim valve.

68mm trim valve

•

Maxitrol 210DZ regulator

L-Series Trim Valve

The L-Series trim valve has a flapper that opens and closes to control the amount of fuel under load. This control uses the same type of program as the L-

Series governor.

68mm Venturi

The 68mm venturi has no moving parts inside of it.

Maxitrol 210DZ regulator

Inlet pressure 10 inH20

Outlet pressure .3 inH20

This regulator is considered a zero pressure. You will not feel any pressure when the lock off is opened. It is not field adjustable.

Fuel is trimmed at idle by a vacuum line going to the top of the regulator

•

•

•

•

Common items to all fuel systems

MAP sensor

02 Sensors

Temperature sensor

Oil pressure sensor

Map Sensor

The map sensor measures both engine vacuum and barometric pressure. It also measures inlet air temperature

.

02 Sensor

The 02 sensors are located in the exhaust system before and after the catalyst. These are both heated sensors.

The precat sensor is always on and the post cat comes on up to 3 mins after the engine starts

No results