Code No. U1000: OSS CAN time-out


caution If diagnosis code No.U1000 is set in the heater controller assembly (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 OSS-ECU via the CAN bus lines. If the ECU cannot receive any of the air conditioner control-related signals from the OSS-ECU, diagnosis code U1000 will be stored.

COMMENTS ON TROUBLE SYMPTOM
Current trouble
  • Connector(s) or wiring harness in the CAN bus lines between the OSS-ECU and the heater controller assembly (A/C-ECU), the power supply system to the OSS-ECU, the OSS-ECU itself, or the heater controller assembly (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 heater controller assembly (A/C-ECU) and the OSS-ECU, and the power supply system to the OSS-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 U0184 (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 audio
  • 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 audio-related diagnosis code is set.

Q. Is the diagnosis code set?
Diagnose the audio. 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.

  • Combination meter
    U1000: OSS CAN 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 OSS-ECU, and then go to Step 6.
A poor connection, open circuit or other intermittent malfunction in the CAN bus line between the OSS-ECU 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 OSS-ECU 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.
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.