Code No. U1000:
OSS CAN time-out
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If diagnosis code No.U1000 is stored in the heater controller
assembly (A/C-ECU), diagnose the CAN main bus line.
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Whenever the ECU is replaced, ensure that the communication
circuit is normal.
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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.
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COMMENTS ON TROUBLE SYMPTOM
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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.
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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
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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 stored regarding
the CAN communication-linked ECUs (Refer to GROUP 54C - CAN Bus Line Diagnostic Flow ).
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If the ignition switch is turned to the ON position without starting
the engine, the diagnosis code U0184 (past trouble) may be stored in the heater controller assembly (A/C-ECU)
after three minutes.
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- Damaged wiring harness or connectors
- Malfunction of the OSS-ECU
- Malfunction of the heater controller assembly (A/C-ECU)
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STEP 1. M.U.T.-III CAN bus diagnostics
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Use the M.U.T.-III to diagnose the CAN bus lines.
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Q.
Is the check result normal?
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 Go to Step 2.
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 Repair the CAN bus lines (Refer to GROUP 54C, Troubleshooting ).
On completion, go to Step 6.
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STEP 2. M.U.T.-III other system diagnosis code
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Check whether the OSS-ECU-related diagnosis code is stored.
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Q.
Is the diagnosis code stored?
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Diagnose the OSS-ECU (Refer to GROUP 42B - Troubleshooting ).
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Go to Step 3.
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STEP 3. M.U.T.-III other system diagnosis code
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Check if a diagnosis code, which relates to CAN communication-linked systems below, is stored.
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- ETACS-ECU
U1000: OSS CAN timeout
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Q.
Is the diagnosis code stored?
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Go to Step 4.
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Go to Step 5.
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STEP 4. Check whether the diagnosis code is stored again.
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Recheck if the diagnosis code is stored.
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(1)Erase the diagnosis code.
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(2)Ignition switch: LOCK (OFF) to ON
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(3)Check if the diagnosis code is stored.
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Q.
Is the diagnosis code stored?
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Replace the OSS-ECU, and then go to Step 6.
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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 ).
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STEP 5. Check whether the diagnosis code is stored again.
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Recheck if the diagnosis code is stored.
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(1)Erase the diagnosis code.
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(2)Ignition switch: LOCK (OFF) to ON
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(3)Check if the diagnosis code is stored.
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Q.
Is the diagnosis code stored?
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Replace the heater controller assembly (A/C-ECU), and then go to Step 6.
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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 ).
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STEP 6. Check whether the diagnosis code is stored again.
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Recheck if the diagnosis code is stored.
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(1)Erase the diagnosis code.
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(2)Ignition switch: LOCK (OFF) to ON
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(3)Check if the diagnosis code is stored.
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Q.
Is the diagnosis code stored?
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Return to Step 1.
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The procedure is complete.
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