Code No. U1000: OSS CAN time-out


caution If diagnosis code No.U1000 stored 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 JUDGEMENT


The heater controller assembly (A/C-ECU) will store diagnosis code U1000 when it can receive no signals from the OSS-ECU.

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 cannot 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 stored regarding the CAN communication-linked ECUs (Refer to GROUP 54C - CAN Bus Line Diagnostic Flow ).

PROBABLE CAUSES



  • Damaged wiring harness or connectors
  • Malfunction of the OSS-ECU
  • 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 OSS-ECU-related diagnosis code is stored.

Q. Is the diagnosis code stored?

Diagnose the OSS-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 stored.

  • ETACS-ECU
    U1000: OSS CAN timeout

Q. Is the diagnosis code stored?

Go to Step 4.
Go to Step 5.

STEP 4. Check whether the diagnosis code is stored again.


Recheck if the diagnosis code is stored.
(1)Erase the diagnosis code.
(2)Turn the power supply mode of the electric motor switch to ON.
(3)Check if the diagnosis code is stored.

Q. Is the diagnosis code stored?

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 stored again.


Recheck if the diagnosis code is stored.
(1)Erase the diagnosis code.
(2)Turn the power supply mode of the electric motor switch to ON.
(3)Check if the diagnosis code is stored.

Q. Is the diagnosis code stored?

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 stored again.


Recheck if the diagnosis code is stored.
(1)Erase the diagnosis code.
(2)Turn the power supply mode of the electric motor switch to ON.
(3)Check if the diagnosis code is stored.

Q. Is the diagnosis code stored?

Return to Step 1.
The procedure is complete.