If diagnosis code No.U0168 is set in the A/C-ECU, diagnose
the CAN main bus line.
caution
Whenever the ECU is replaced, ensure that the communication
circuit is normal.
TROUBLE JUDGMENT
The heater controller assembly (A/C-ECU) receives air conditioner control-related signals
from the KOS via the CAN bus lines. If the ECU cannot receive any of the air conditioner control-related
signals from the KOS, diagnosis code U0168 will be stored.
COMMENTS ON TROUBLE SYMPTOM
Current trouble
Connector(s) or wiring harness in KOS the CAN bus lines between the WCM and the
heater controller assembly (A/C-ECU), the power supply system to the WCM, the WCM itself, or
the A/C-ECU may be faulty.
Past trouble
Carry out diagnosis with particular emphasis on connector(s) or wiring harness in
the CAN bus lines between the heater controller assembly (A/C-ECU) and the WCM, and the power
supply system to the WCM. For diagnosis procedures, refer to "How to treat past trouble" (Refer
to GROUP 00 - How to Treat Past Trouble ).?
note
For a past trouble, you can not find it by the M.U.T.-III CAN bus diagnostics even if
there is any failure in CAN bus lines. In this case, refer to GROUP 00, How to Cope with Intermittent
Malfunction and check the CAN bus lines. You can narrow
down the possible cause of the trouble by referring to the diagnosis code, which is set regarding
the CAN communication-linked ECUs (Refer to GROUP 54C - CAN Bus Line Diagnostic Flow ).
caution
If the ignition switch is turned to the ON position without starting
the engine, the diagnosis code U0168 (past trouble) may be set to the heater controller assembly
(A/C-ECU) after three minutes.
PROBABLE CAUSES
Damaged wiring harness or connectors
Malfunction of the KOS
Malfunction of the heater controller assembly (A/C-ECU)
DIAGNOSIS PROCEDURE
STEP 1. M.U.T.-III CAN bus diagnostics
Use the M.U.T.-III to diagnose the CAN bus lines.
Q.
Is the check result normal?
Go to Step 2.
Repair the CAN bus lines (Refer to GROUP 54C Troubleshooting ).
On completion, go to Step 6.
STEP 2. M.U.T.-III other system diagnosis code
Check whether the KOS-related diagnosis code is set.
Q.
Is the diagnosis code set?
Diagnose the KOS. (Refer to GROUP 42B "Symptom chart").
Go to Step 3.
STEP 3. M.U.T.-III other system diagnosis code
Check if a diagnosis code, which relates to CAN communication-linked systems below, is
set.
ETACS-ECU U0168: KOS timeout
Q.
Is the diagnosis code set?
Go to Step 4.
Go to Step 5.
STEP 4. Check whether the diagnosis code is reset.
Recheck if the diagnosis code is set.
(1)Erase the diagnosis code.
(2)Ignition switch: LOCK (OFF) to ON
(3)Check if the diagnosis code is set.
Q.
Is the diagnosis code set?
Replace the KOS, and then go to Step 6.
A poor connection, open circuit or other intermittent malfunction in the CAN bus
line between the WCM and the heater controller assembly (A/C-ECU) (Refer to GROUP 00 - How
to Cope with Intermittent Malfunction ).
STEP 5. Check whether the diagnosis code is reset.
Recheck if the diagnosis code is set.
(1)Erase the diagnosis code.
(2)Ignition switch: LOCK (OFF) to ON
(3)Check if the diagnosis code is set.
Q.
Is the diagnosis code set?
Replace the heater controller assembly (A/C-ECU), and then go to Step 6.
A poor connection, open circuit or other intermittent malfunction in the CAN bus
line between the WCM and the heater controller assembly (A/C-ECU) (Refer to GROUP 00 - How
to Cope with Intermittent Malfunction ).
STEP 6. Check whether the diagnosis code is reset.
).?
