If there is any problem in the CAN bus lines,
an incorrect diagnosis code may be set. Prior to this diagnosis, always diagnose the CAN bus
lines.
Before replacing the ECU, ensure that the communication circuit is normal.
OPERATION
4WD-ECU monitors the CAN C-bus off interruption, and if any abnormality occurs, it interrupts
the system.
DIAGNOSIS CODE SET CONDITIONS
If the following conditions are met when the system is in operation (always), 4WD-ECU
gradually switches the control from 4WD to 2WD, flashes the 4WD/LOCK indicators alternately,
and sets the diagnosis code No. U0001.
IG1 voltage: 10 V or more
When CAN C-bus off interruption is detected
PROBABLE CAUSES
Current trouble
Wiring harness or connector failure of CAN bus line
4WD-ECU malfunction
Past trouble
Intermittent wiring harness or connector failure
note
For diagnosis procedures, refer to "How to treat past trouble". (Refer
to GROUP 00, How to Treat Past Trouble .)
DIAGNOSIS PROCEDURE
STEP 1. M.U.T.-III CAN bus diagnostics
Use M.U.T.-III to diagnose the CAN bus lines.
Q.
Is the check result normal?
Go to Step 2.
Repair the CAN bus line. (Refer to GROUP 54C -
Troubleshooting .)
Then go to Step 2.
STEP 2. Check the following connector:
Check the connectors below for improper engagement, terminal damage or terminal drawn
in the connector case.
C-130 4WD-ECU connector
C-313, C-317 ETACS-ECU connector
Q.
Are the connectors and terminals in good condition?
Go to Step 3.
Repair the connector(s) or terminal(s). Then go to Step 5.
STEP 3. Wiring harness check
Check the wiring harness between the C-130 4WD-ECU connector and the C-313 ETACS-ECU connector
for damage or other problem.
Q.
Is the wiring harness in good condition?
Go to Step 4.
Repair damage or other problem in the wiring harness. Then go to Step 5.
STEP 4. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Turn the ignition switch from the LOCK (OFF) position to the ON position.
(3)Check if the diagnosis code is set.
Q.
Is the diagnosis code No. U0001 set?
Replace 4WD-ECU. (Refer to .) Then go to Step
5.
The trouble can be an intermittent malfunction such as loose connector fit, wiring
harness open circuit. (Refer to GROUP -
How to Cope with Intermittent Malfunction .)
STEP 5. Check whether the diagnosis code is reset.
)
)
.)
Go to Step 2.
Repair the CAN bus line. (Refer to GROUP 54C -
Troubleshooting