Code No. U1000: OSS/KOS_OSS CAN timeout

caution

If diagnosis code No.U1000 is set in the heater controller assembly (A/C-ECU), diagnose the CAN main bus line.
Whenever the ECU is replaced, ensure that the communication circuit is normal.

TROUBLE JUDGEMENT

The heater controller assembly (A/C-ECU) receives air conditioner control-related signals from the KOS&OSS-ECU via the CAN bus lines. If the ECU cannot receive any of the air conditioner control-related signals from the KOS&OSS-ECU, diagnosis code U1000 will be set.

COMMENTS ON TROUBLE SYMPTOM

Current trouble

Connector(s) or wiring harness in the CAN bus lines between the KOS&OSS-ECU and the heater controller assembly (A/C-ECU), the power supply system to the KOS&OSS-ECU, the KOS&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 KOS&OSS-ECU, and the power supply system to the KOS&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, diagnosis code U1000 (past trouble) may be set in the heater controller assembly (A/C-ECU) after three minutes.

PROBABLE CAUSES

Damaged wiring harness or connectors
Malfunction of the KOS&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 if diagnosis code is set in the KOS&OSS-ECU.

Q. Is the diagnosis code set?

	Diagnose the KOS&OSS-ECU (Refer to GROUP 42B - Troubleshooting ).

	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.

Combination meter
U1000: OSS/KOS_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 set again.

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&OSS-ECU (Refer to GROUP 42B - KOS&OSS-ECU ), and then go to Step 6.

	A poor connection, open circuit or other intermittent malfunction in the CAN bus line between the KOS&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 set again.

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) (Refer to ), and then go to Step 6.

	A poor connection, open circuit or other intermittent malfunction in the CAN bus line between the KOS&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 set again.

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.