[54C] Controller Area Network (CAN)

[54C] Controller Area Network (CAN)
54C-1
GROUP 54C
CONTENTS
GENERAL INFORMATION . . . . . . . .
54C-2
CAN BUS DIAGNOSTICS . . . . . . . . .
STRUCTURE . . . . . . . . . . . . . . . . . . .
54C-2
CAN COMMUNICATION SIGNAL TABLE
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54C-6
OPERATION . . . . . . . . . . . . . . . . . . .
54C-3
SELF-DIAGNOSIS . . . . . . . . . . . . . . .
54C-5
CAN COMMUNICATION-RELATED
DIAGNOSIS CODE (U CODE) TABLE
54C-5
54C-8
CONTROLLER AREA NETWORK (CAN)
54C-2
GENERAL INFORMATION
GENERAL INFORMATION
M2542000100126
CAN, an abbreviation for Controller Area Network, is
an ISO-certified international standard for a serial
multiplex communication protocol*1. A communication circuit employing the CAN protocol connects
each ECU, and sensor data can be shared among,
which enables more reduction in wiring.
NOTE: *1: The regulations have been decided in
detail, from software matters such as the necessary
transmission rate for communication, the system,
data format, and communication timing control
method to hardware matters such as the harness
type and length and the resistance values.
CAN offers the following advantages.
• Transmission rates are much faster than those in
conventional communication (up to 1 Mbps),
allowing much more data to be sent.
• It is exceptionally immune to noise, and the data
obtained from each error detection device is more
reliable.
• Each ECU connected via the CAN communicates
independently, therefore if the ECU enters damaged mode, communications can be continued in
some cases.
STRUCTURE
M2542000200123
ABS-ECU
<without active stability control system>
or
ABS/Active stability control system-ECU
<with active stability control system>
Electric
power
steeringECU
A/C-ECU
Multi-centre
display
Terminal resistor
CAN_H
Main bus lines
Engine-ECU <M/T>
or engineA-M/T-ECU
<Automated
manual
transmission>
Combination
meter
CAN_L
G and yaw
rate sensor
Steering
wheel
sensor
SRS-ECU
ETACSECU
Diagnosis
connector
MUT-III
: shows main bus line.
: shows sub bus line.
AC312894AB
• The CAN bus line consists of two lines, CAN_L
and CAN_H (CAN Low and CAN High, respectively), as well as two terminal resistors (A
twisted-pair cable, highly resistant to noise, is
used for the communications line).
• The CAN bus line connecting the two terminal
resistors is the main bus line, and the CAN bus
line connecting each ECU is the sub-bus line.
• The terminal resistors are installed in the
engine-ECU <M/T> or the engine-A-M/T-ECU
<Automated manual transmission> module and
connection meter to stabilize communication signals (The terminal resistance is set at approximately 120 Ω).
• A maximum of 10 ECUs are connected in the
COLT CAN bus line as follows.
• Engine-ECU <M/T>
CONTROLLER AREA NETWORK (CAN)
54C-3
OPERATION
• Engine-A-M/T-ECU* <Automated manual
transmission>
• ABS-ECU <Vehicles without active stability
control system>
• ABS/Active stability control system-ECU
<Vehicles with active stability control system>
• Steering wheel sensor <Vehicles with active
stability control system>
• G and yaw rate sensor <Vehicles with active
stability control system>
• Electric power steering-ECU
• SRS-ECU
• A/C-ECU
• ETACS-ECU
• Multi-centre display
• Combination meter
NOTE: Engine-A-M/T-ECU*: Engine automated manual transmission electronic control unit
OPERATION
M2542000300131
Data frames
A
A
A
A
ECU-1
Interval "a"
B
B
B
ECU-1
Transmission
suspended by
mediation
Interval "b"
C
C
C
ECU-2
Interval "c"
A
B
C
A
Retransmission
B
A
C
B
A
CAN bus
AC206267
AC206267AD
The CAN communication system is described below.
• Each ECU communicating with CAN periodically
sends several sensors’ information on CAN bus
as data frame (called periodical sending data).
For further details, consult the data frame section.
• ECUs requiring data on CAN bus can receive
data frames sent from each ECU simultaneously.
• The data sent from each ECU conducting CAN
communication is transmitted at 10-1000msec
interval depending on necessity of data.
NOTE: In the figure above, the data frame A is transmitted in "a" intervals, while the data frames B
and C are transmitted at intervals "b" and "c,"
respectively.
• A single ECU transmits multiple data frames.
• When data frames conflict with one another
(when plural ECUs transmit signals simultaneously), data is prioritised for transmission by
mediation, therefore, plural data frames are not
sent simultaneously. For further details, consult
the mediation section.
• Data is transmitted not by the conventional voltage-using method but by voltage potential difference. For further details, consult the section on
CAN bus voltage transformation .
• Reliability of each ECU transmitting signals via
CAN communication is secured by several error
detection and recovery processes. For further
details, consult the sections on error detection
and system recovery.
• For major communication signals (transmitting
signals) among ECUs, refer to P.54C-6.
CONTROLLER AREA NETWORK (CAN)
54C-4
OPERATION
MEDIATION
Because each ECU transmits data independently on
the CAN bus, there are cases of data collision when
multiple data frames that ECUs attempt to transmit
simultaneously (if multiple ECUs transmit at nearly
the same moment). At this moment, processing of
the ECUs attempting transmission is performed in
the following way.
1. Data frame with high priority is transmitted first
according to ID codes memorized in data frames.
2. Transmission of low-priority data (data frames) is
suspended by the issuing ECUs until the bus
clears (when no transmission data exists on the
CAN bus).
NOTE: If the suspended state continues for a specific time, new data (data frame content) is created and sent.
3. ECU containing suspended data frames transmits the data when the bus becomes available.
NOTE: There is enough capacity on the CAN bus,
which never prevents data frames from being sent.
VOLTAGE TRANSFORMATION ON THE
CAN BUS
Voltage
transformation
in CAN_H
3.5 V
Voltage
transformation
in CAN_L
2.5 V
1.5 V
State:
Recessive
Dominant
Recessive
0
Logic value:
1
AC204753AC
Data frame transmission through the CAN bus line
involves voltage transformation (for output signals) in
the distinctive CAN profile as follows. The ECU
transmitting through the CAN_H and CAN_L bus
lines sends 2.5-3.5V signals to the CAN_H side and
2.5-1.5V signals to the CAN_L side. The receiving
ECU reads the data from the CAN_H and CAN_L
potential difference. "Recessive" refers to the state
where both CAN_H and CAN_L are under the 2.5-V
state, and "Dominant" refers to the state where
CAN_H is under the 3.5-V state and CAN_L is under
the 1.5-V state. By transformation mainly to 2.5V,
even in cases when voltage is rendered 0 from faulty
grounding or the like (causing a problem of an
approximate 0.5 voltage increase on the communications line), communication can be continued uninterrupted. Employing dual communications lines
improves reliability to prevent the presence of noise,
compared to the conventional communication
method.
DATA FRAMES
Data Frames
S
O
F
ID region
Control
region
Data region
CRC
ACK
E
region
region
O
F
AC204754
AC204754AC
CONTROLLER AREA NETWORK (CAN)
SELF-DIAGNOSIS
SOF (Start of Frame)
• Indicates the start of the frame
ID (Identifier) region
• Identifies the data content while specifying priority rank in case of mediation
Control region
• Specifies the frame type, data length, etc.
Data region
• Values used for data control, etc.
Cyclic Redundancy Check (CRC) region
• Region where to check for errors in sent data The
transmitting ECU calculates data regions by
applying prescribed operations and stores the
results. The receiving ECU detects erroneous
communication by comparing the CRC region
with the data region.
54C-5
ACK (Acknowledge) region
• Region where to conform the reception of sent
data
EOF(End of Frame)
• Indicates the end of the frame
ERROR DETECTION AND RECOVERY
CAN protocol secures its reliability of communication
by providing several error detection function such as
CRC shown in data frame, and the recovery function
(recovery is performed by resending, from abnormal
state such as transmission errors). If an error is
detected but it is not resolved even after recovery,
communication is stopped. This state is called "Bus
Off."
SELF-DIAGNOSIS
• CAN self-diagnosis is performed by each ECU
connected to the CAN bus.
• Diagnostic trouble codes related to communication are named with the capital letter U, and are
called "U-codes."
• A summary of the CAN self-diagnosis system is
presented below. For further details on each
diagnosis code stored by the ECUs, consult the
U-Code Diagnostic Trouble Code List P.54C-8.
TIMEOUT
Each ECU transmits data frames periodically. If the
intended receiving ECU cannot receive the data
frame within the specified period, it sets a diagnosis
code indicating communication timeout for the ECU
that failed to transmit. A data length is assigned to
each data frame. If a data length is shorter or longer
than the specified, the ECU cannot receive the data.
M2542000400138
BUS OFF
Related to a communication error that persists even
after the transmitting ECU attempts recovery for a
specified number of attempts or that persists for a
specified period after recovery. Communication is
stopped and this diagnostic code is issued.
FAILURE DATA
When the transmitting ECU detects failure of a sensor directly connected to it, this is the pertinent data
used to inform the ECU.
DYNAMIC RANGE ERROR
When the data received exceeds or is less than the
prescribed range, this diagnosis code is issued.
CAN BUS DIAGNOSTICS
M2542000500157
As ECUs are connected via CAN bus (including
MUT-III), always diagnose CAN bus to confirm its
normality when inspecting. Simply by performing
MUT-III screen operations, the following inspections
can be performed automatically, and the result can
be used to verify the CAN bus status.
• Voltage measurement between the CAN_L and
CAN_H and the body grounding terminal
• Resistance measurement between the CAN_L
and CAN_H
• Confirmation of communication of all ECUs
CONTROLLER AREA NETWORK (CAN)
54C-6
CAN COMMUNICATION SIGNAL TABLE
CAN COMMUNICATION SIGNAL TABLE
M2542000600143
• D: Engine-ECU <M/T> or Engine-transmission-ECU <Automated manual transmission>
• E: Combination meter
• F: A/C-ECU
• G: Electric power steering-ECU
• H: Centre display unit
• I: ETACS-ECU
• J: SRS-ECU
• Aa: ABS-ECU <Vehicles without active stability
control system>
• Ab: ABS/Active stability control system-ECU
<Vehicles with active stability control system>
• B: G and yaw rate sensor <Vehicles with active
stability control system>
• C: Steering wheel sensor <Vehicles with active
stability control system>
SIGNAL
TRANS RECEIVER ECU
MITTER Aa Ab B
C
ECU
D
E
F
G
H
I
J
Aa or Ab −
−
−
−
•
•
−
−
−
−
−
ABS indicator warning lamp
request signal
−
−
−
−
−
•
−
−
−
−
−
Active stability control
information lamp request signal
−
−
−
−
−
•
−
−
−
−
−
EBD fault or brake fluid level too
low signal
−
−
−
−
−
•
−
−
−
−
−
Brake light switch signal
−
−
−
−
•
−
−
−
−
−
−
Brake switch signal
−
−
−
−
•
−
−
−
−
−
−
Front wheel speed signal
−
−
−
−
•
•
−
•
−
−
−
Rear wheel speed signal
−
−
−
−
•
•
−
−
•
−
−
Rear left side wheel speed signal
for cruise control
−
−
−
−
•
−
−
−
−
−
−
Target gear request signal
−
−
−
−
•
−
−
−
−
−
−
System signal
−
−
−
−
•
−
−
−
−
−
−
Active stability control system
brake action signal
−
−
−
−
•
−
−
−
−
−
−
Brake torque adjust signal
−
−
−
−
•
−
−
−
−
−
−
Brake pedal condition signal
−
−
−
−
•
−
−
−
−
−
−
Clutch condition signal <Active
stability control system>
−
−
−
−
•
−
−
−
−
−
−
Engine torque request signal
−
−
−
−
•
−
−
−
−
−
−
Vehicle transversal acceleration
at gravity centre
−
−
−
−
•
−
−
−
−
−
−
−
•
−
−
−
−
−
−
−
−
−
−
•
−
−
−
−
−
−
−
−
−
−
•
−
−
−
−
−
−
−
−
−
−
•
−
−
−
−
−
−
−
−
−
Parking brake signal
Yaw rate signal
B
Lateral gravity signal
Steering wheel angle signal
Steering wheel angle rotation
speed signal
C
CONTROLLER AREA NETWORK (CAN)
54C-7
CAN COMMUNICATION SIGNAL TABLE
SIGNAL
TRANS RECEIVER ECU
MITTER Aa Ab B
C
ECU
D
E
F
G
H
I
J
−
−
−
−
−
−
−
−
−
•
−
A/C information signal
−
−
−
−
−
−
•
−
−
−
−
Engine condition signal
−
−
−
−
−
−
−
−
−
•
−
Engine torque signal
−
•
−
−
−
−
−
−
−
−
−
Engine warning buzzer request
signal
−
−
−
−
−
−
−
−
−
•
−
Accelerator pedal condition
signal
−
•
−
−
−
−
−
−
−
−
−
Clutch switch signal <M/T>
−
•
−
−
−
−
−
−
−
−
−
Clutch condition signal
−
•
−
−
−
−
−
−
−
−
−
Engine speed signal
−
•
−
−
•
•
−
•
−
−
−
Malfunction indicator lamp
request signal
−
−
−
−
−
•
−
−
−
−
−
Engine coolant temperature
signal
−
−
−
−
−
•
−
−
−
−
−
Fuel consumption signal
−
−
−
−
−
−
−
−
•
−
−
Fan relay control signal
−
−
−
−
−
−
−
−
−
•
−
Selector position signal
<Automated manual
transmission>
−
•
−
−
−
•
−
−
−
•
−
Kick down signal
−
•
−
−
−
−
−
−
−
−
−
Lost torque signal
−
•
−
−
−
−
−
−
−
−
−
−
−
−
−
•
−
−
−
•
−
−
Vehicle speed signal
−
−
−
−
•
−
−
−
−
−
−
Environment temperature signal
−
−
−
−
•
−
•
−
•
•
−
Odometer signal
−
−
−
−
•
−
−
−
−
•
−
Communication continuation
request signal
−
−
−
−
−
−
−
−
−
•
−
Seat belt buzzer request signal
−
−
−
−
−
−
−
−
−
•
−
−
−
−
−
•
−
−
−
−
−
−
Increacing idle speed signal
−
−
−
−
•
−
−
−
−
−
−
Cooling fan request signal
−
−
−
−
•
−
−
−
−
−
−
Air conditioner refrigerant
pressure signal
−
−
−
−
•
−
−
−
−
−
−
Air conditioner compressor drive
duty signal
−
−
−
−
•
−
−
−
−
−
−
−
−
−
−
•
−
−
−
−
−
−
−
−
−
−
•
•
−
−
−
−
−
Immobilizer signal
Fuel information signal
Air conditioner switch signal
Motor current signal
Electric power steering fail lamp
signal
D
E
F
G
CONTROLLER AREA NETWORK (CAN)
54C-8
CAN COMMUNICATION-RELATED DIAGNOSIS CODE (U CODE) TABLE
SIGNAL
TRANS RECEIVER ECU
MITTER Aa Ab B
C
ECU
D
E
F
G
H
I
J
−
−
−
−
−
−
−
−
−
•
−
Ignition switch (ACC) signal
−
−
−
−
−
−
−
−
−
•
−
Communication continuation
request signal
−
−
−
−
−
−
−
−
−
•
−
−
−
−
−
•
−
−
−
−
−
−
Ignition switch (IG1) signal
−
−
−
−
−
•
−
−
−
−
−
Illumination signal
−
−
−
−
•
•
−
−
•
−
−
Fog light indicator request signal
−
−
−
−
−
•
−
−
−
−
−
Column switch condition signal
−
−
−
−
−
•
−
−
−
−
−
Door switch condition signal
−
−
−
−
•
•
−
−
−
−
−
Instruction to enter CAN sleep
mode signal
−
−
−
−
−
•
−
−
−
−
−
ETACS plausibility signal
−
−
−
−
•
−
−
−
−
−
−
Daytime running lights condition
signal
−
−
−
−
•
−
−
−
−
−
−
−
−
−
−
−
•
−
−
−
−
−
Door unlock request signal
−
−
−
−
•
−
−
−
−
−
−
Engine stop request signal
−
−
−
−
•
−
−
−
−
−
−
Buzzer sound signal
H
Immobilizer signal
I
SRS warning lamp illumination
request signal
J
CAN COMMUNICATION-RELATED DIAGNOSIS CODE (U
CODE) TABLE
M2542000700128
OUTPUT ECU
CODE
NO.
DIAGNOSTIC ITEM
ACTION
Engine-ECU
<M/T> or
Engine-A-M/TECU
<Automated
manual
transmission>
U1073
Bus Off
CAN main bus line diagnostics
U1102
ABS or ASC/Active stability control
system-ECU time-out
U1106
Electric power steering-ECU
U1108
Combination meter time-out
U1109
ETACS-ECU time-out
U1110
A/C-ECU time-out
U1112
SRS-ECU time-out
U1073
Bus Off
ABS-ECU
CAN main bus line diagnostics
CONTROLLER AREA NETWORK (CAN)
CAN COMMUNICATION-RELATED DIAGNOSIS CODE (U CODE) TABLE
OUTPUT ECU
CODE
NO.
ABS/Active
U1073
stability control U1100
system-ECU
54C-9
DIAGNOSTIC ITEM
ACTION
Bus Off
CAN main bus line diagnostics
Engine-ECU <M/T> or engine-A-M/T-ECU
<Automated manual transmission> time-out
(related to engine)
U1101
Engine-A-M/T-ECU time-out (related to
automated manual transmission)
U1104
Steering wheel sensor time-out
U1105
G and yaw rate sensor time-out
U1108
Combination meter time-out
U1109
ETACS-ECU time-out
U1406
Failure information on engine-A-M/T-ECU
(related to engine)
U1413
Failure information on engine-A-M/T-ECU
(related to automated manual transmission)
U1426
Failure information on engine-A-M/T-ECU
(related to engine)
U1427
Failure information on engine-A-M/T-ECU
(related to engine)
U1428
Failure information on engine-A-M/T-ECU
(related to engine)
U1429
Failure information on engine-A-M/T-ECU
(related to engine)
U1430
Failure information on engine-A-M/T-ECU
(related to engine)
U1431
Failure information on engine-A-M/T-ECU
(related to automated manual transmission)
Steering wheel
sensor
U1073
Bus Off
CAN main bus line diagnostics
Combination
meter
U1073
Bus Off
CAN main bus line diagnostics
U1100
Engine-ECU <M/T> or engine-A-M/T-ECU
<Automated manual transmission> time-out
(related to engine)
U1101
Engine-A-M/T-ECU time-out (related to
automated manual transmission)
U1102
ABS or ASC/Active stability control
system-ECU time-out
U1109
ETACS-ECU time-out
U1120
Failure information on engine-ECU <M/T> or Diagnose CAN main bus lines
engine-A-M/T-ECU <Automated manual
and confirm input signals.
transmission> (related to engine)
Diagnose CAN main bus lines
and confirm input signals.
54C-10
CONTROLLER AREA NETWORK (CAN)
CAN COMMUNICATION-RELATED DIAGNOSIS CODE (U CODE) TABLE
OUTPUT ECU
CODE
NO.
DIAGNOSTIC ITEM
ACTION
Multi-centre
display unit
(middle-grade
type)
U1073
Bus Off
CAN main bus line diagnostics
U1100
Engine-ECU <M/T> or engine-A-M/T-ECU
<Automated manual transmission> time-out
(related to engine)
U1101
Engine-A-M/T-ECU time-out (related to
automated manual transmission)
U1108
Combination meter time-out
U1109
ETACS-ECU time-out
U1110
A/C-ECU time-out
U1120
Failure information on engine-ECU <M/T> or Diagnose CAN main bus lines
engine-A-M/T-ECU <Automated manual
and confirm input signals.
transmission> (related to engine)
U1128
Failure information on combination meter
U1130
Failure information on A/C-ECU
U1073
Bus Off
U1100
Engine-ECU <M/T> or engine-A-M/T-ECU
<Automated manual transmission> time-out
(related to engine)
U1101
Engine-A-M/T-ECU time-out (related to
automated manual transmission)
U1102
ABS or ASC/Active stability control
system-ECU time-out
U1108
Combination meter time-out
U1111
Multi-centre display unit (middle-grade type)
time-out
U1112
SRS-ECU time-out
U1121
Failure information on engine-A-M/T-ECU
(related to automated manual transmission)
U1128
Failure information on combination meter
U1073
Bus Off
U1100
Powertrain control module time-out (related
to engine)
U1108
Combination meter time-out
U1109
ETACS-ECU time-out
ETACS-ECU
A/C-ECU
CAN main bus line diagnostics
Diagnose CAN main bus lines
and confirm input signals.
CAN main bus line diagnostics
CONTROLLER AREA NETWORK (CAN)
CAN COMMUNICATION-RELATED DIAGNOSIS CODE (U CODE) TABLE
54C-11
OUTPUT ECU
CODE
NO.
DIAGNOSTIC ITEM
ACTION
Electric power
steering-ECU
U1073
Bus Off
CAN main bus line diagnostics
U1100
Engine-ECU <M/T> or engine-A-M/T-ECU
<Automated manual transmission> time-out
(related to engine)
U1102
ABS or ASC/Active stability control
system-ECU time-out
U1120
Failure information on engine-ECU <M/T> or
engine-A-M/T-ECU <Automated manual
transmission> (related to engine)
U1122
Failure information on ABS or active stability
control system-ECU
Diagnose CAN main bus lines
and confirm input signals.
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