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DTC U0168: WCM/F.A.S.T. CAN timeout
cautionIf DTC U0168 is set in the A/C-ECU, diagnose the CAN main bus line.
cautionWhenever the ECU is replaced, ensure that the communication circuit is normal.
 
 
 
 
DTC SET CONDITION
The heater controller assembly (A/C-ECU) receives air conditioning control-related signals from the KOS-ECU via the CAN bus lines. If the ECU cannot receive any of the air conditioning control-related signals from the KOS-ECU, DTC U0168 will be set.
 
 
TECHNICAL DESCRIPTION (COMMENT)
Current trouble
  • Connector(s) or wiring harness in the CAN bus lines between the KOS-ECU and the heater controller assembly (A/C-ECU), the power supply system to the KOS-ECU, the KOS-ECU itself, or the heater controller assembly (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 KOS-ECU, and the power supply system to the KOS-ECU. For diagnostic procedures, refer to "How to treat past trouble" (Refer to GROUP 00 - How to Treat Past Trouble ).
    noteFor a past trouble, you can not find it by the M.U.T.-IIISE 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 DTC, which is set regarding the CAN communication-linked ECUs (Refer to GROUP 54C - CAN Bus Line Diagnostic Flow ).
    cautionIf the electric motor switch is turned to the ON position without starting the engine, DTC U0168 (past trouble) may be set in the heater controller assembly (A/C-ECU) after three minutes.
 
 
TROUBLESHOOTING HINTS
  • The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector
  • Malfunction of the KOS-ECU
  • Malfunction of the heater controller assembly (A/C-ECU)
 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-IIISE), diagnose CAN bus line.
(1)
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn the electric motor switch to the OFF position before connecting or disconnecting scan tool (M.U.T.-IIISE).
Connect scan tool (M.U.T.-IIISE). Refer to "How to connect the Scan Tool (M.U.T.-IIISE) ".
(2) Turn the electric motor switch to the ON position.
(3) Diagnose the CAN bus line.
(4) Turn the electric motor switch to the OFF position.
Is the CAN bus line found to be normal?
Go to Step 2.
Repair the CAN bus lines (Refer to GROUP 54C, Troubleshooting ).
 
STEP 2. Using scan tool (M.U.T.-IIISE), check whether the other system DTC is set.
Check whether the KOS-related DTC is set.
Is the DTC set?
Diagnose the KOS (Refer to GROUP 42B, Troubleshooting ).
Go to Step 3.
 
STEP 3. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again.
Check the DTC, which relates to CAN communication-linked systems below, is set.
  • ETACS-ECU
    U0168: WCM/F.A.S.T CAN timeout
Is the DTC set?
Go to Step 4.
Go to Step 5.
 
STEP 4. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again.
Recheck the DTC.
(1) Erase the DTC.
(2) Electric motor switch: OFF to ON
(3) Check the DTC.
Is the DTC set?
Replace the KOS-ECU.
A poor connection, open circuit or other intermittent malfunction in the CAN bus line between the KOS-ECU and the heater controller assembly (A/C-ECU) (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
 
STEP 5. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again.
Recheck the DTC.
(1) Erase the DTC.
(2) Electric motor switch: OFF to ON
(3) Check the DTC.
Is the DTC set?
Replace the heater controller assembly (A/C-ECU).
A poor connection, open circuit or other intermittent malfunction in the CAN bus line between the KOS-ECU and the heater controller assembly (A/C-ECU) (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).