Code No. U0151: SRS CAN communication time-out


caution If diagnosis code No.U0151 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 A/C-ECU receives air conditioner control-related signals from the SRS-ECU via the CAN bus lines. If the ECU cannot receive any of the air conditioner control-related signals from the SRS-ECU, diagnosis code U0151 will be stored.

COMMENTS ON TROUBLE SYMPTOM
Current trouble
  • Connector(s) or wiring harness in the CAN bus lines between the SRS-ECU and the A/C-ECU, the power supply system to the SRS-ECU, the SRS-ECU itself, or the A/C-ECU may be defective.
Past trouble
  • Carry out diagnosis with particular emphasis on connector(s) or wiring harness in the CAN bus lines between the SRS-ECU and the A/C-ECU, and the power supply system to the SRS-ECU. 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 U0151 (past trouble) may be set to the A/C-ECU after three minutes.

PROBABLE CAUSES

  • Damaged harness wires and connectors
  • Malfunction of SRS-ECU
  • Malfunction of the 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 SRS-related diagnosis code is set.

Q. Is the diagnosis code set?
Diagnose the SRS-ECU. Refer to .
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
    U0151: SRS-ECU-related time-out diagnosis code

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 SRS-ECU, and then go to Step 6.
A poor connection, open circuit or other intermittent malfunction in the CAN bus line between the SRS-ECU and the 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 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 SRS-ECU and the A/C-ECU (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).

STEP 6. 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?
Return to Step 1.
The procedure is complete.