System
Can communication system
Can communication system : system description
CAN (Controller Area Network) is a serial communication line for real time application. It is an on-vehicle multiplex communication line with high data communication speed and excellent error detection ability. Many electronic control units are equipped onto a vehicle, and each control unit shares information and links with other control units during operation (not independent). In CAN communication, control units are connected with 2 communication lines (CAN-H line, CAN-L line) allowing a high rate of information transmission with less wiring.
Each control unit transmits/receives data but selectively reads required data only.
Diag on can
Diag on can : system description
System diagram
Description
“Diag on CAN” is a diagnosis method which uses the CAN communication line for the communication between the control unit and the diagnostic tool.
Trouble diagnosis
Component description
Component | Description |
Main line | CAN communication line between splices |
Branch line | Can communication line between splice and a control unit |
Splice | A point connecting a branch line with a main line |
Termination circuit | Circuit connected across the CAN communication system. (Resistor) |
Condition of error detection
DTC (e.g. U1000 and U1001) of CAN communication is indicated on SELF-DIAG RESULTS on CONSULT if a CAN communication signal is not transmitted or received between units for 2 seconds or more.
Can communication system error
When dtc of can communication is indicated even though can communication system is normal
Note:
Can communication system is normal if dtc of can communication is indicated on self-diag results of consult under the above conditions. Erase the memory of the self-diagnosis of each control unit.
Symptom when error occurs in can communication system
In CAN communication system, multiple control units mutually transmit and receive signals. Each control unit cannot transmit and receive signals if any error occurs on CAN communication line. Under this condition, multiple control units related to the root cause malfunction or go into fail-safe mode.
Error example
Note:
Each vehicle differs in symptom of each control unit under fail-safe mode and can communication line wiring.
Example: main line between data link connector and abs actuator and electric unit (control unit) open circuit
Unit name | Major symptom |
ECM | Engine torque limiting is affected, and shift harshness increases. |
Bcm |
|
Eps control unit | The steering effort increases. |
Combination meter |
|
Abs actuator and electric unit (control unit) | Normal operation. |
Tcm | No impact on operation. |
Ipdm e/r | When the ignition switch is on,
|
Example: tcm branch line open circuit
Unit name | Major symptom |
Ecm | Engine torque limiting is affected, and shift harshness increases. |
BCM | Reverse warning buzzer does not sound. |
Eps control unit | Normal operation. |
Combination meter |
|
Abs actuator and electric unit (control unit) | Normal operation. |
Tcm | No impact on operation. |
IPDM E/R | Normal operation. |
Note:
The model (all control units on CAN communication system are Diag on CAN) cannot perform CAN diagnosis with CONSULT if the following error occurs. The error is judged by the symptom.
Error | Difference of symptom |
Data link connector branch line open circuit | Normal operation. |
Can-h, can-l harness short-circuit | Most of the control units which are connected to the can communication system enter fail-safe mode or are deactivated. |
Example: data link connector branch line open circuit
Note:
When data link connector branch line is open, transmission and reception of CAN communication signals are not affected. Therefore, no symptoms occur. However, be sure to repair malfunctioning circuit.
Example: can-h, can-l harness short circuit
Can diagnosis with consult
Can diagnosis on consult extracts the root cause by receiving the following information.
Self-diagnosis
If communication signals cannot be transmitted or received among control units communicating via CAN communication line, CAN communication-related DTC is displayed on the CONSULT “Self Diagnostic Result” screen.
Note:
The following table shows examples of CAN communication-related DTC. For other DTC, refer to the applicable sections.
Can diagnostic support monitor
Monitor item (consult)
Example: can diag support mntr indication
Without past
With past
How to use can communication signal chart
The can communication signal chart lists the signals transmitted/received among control units. It is useful for detecting the root cause by finding a signal related to the symptom, and by checking transmission and reception unit.
Power supply and ground circuit
Av control unit
Av control unit : diagnosis procedure
Regarding Wiring Diagram information, refer to AV-234, "Wiring Diagram".
1.Check fuse
Check that the following fuses are not blown.
Are the fuses blown?
Yes >> replace the blown fuse after repairing the affected circuit.
...
The seat belt reminder warning
continues sounding, or does not
sound
Description
Seat belt reminder warning does not sound.
Seat belt reminder warning sounds continuously.
Diagnosis procedure
1.Check seat belt warning lamp
Turn ignition switch on.
Check the operation of the seat belt warning lamp in the combination
meter.
Is the inspection ...
P099C Shift solenoid G
DTC Logic
DTC
CONSULT screen terms
(Trouble diagnosis content)
DTC detection condition
Possible causes
P099C
SHIFT SOLENOID G
(Shift Solenoid G Control Circuit
High)
The TCM high clutch & reverse brake solenoid
valve current monitor reading is 200 mA ...