Code No.U1100
Engine CAN timeout
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If diagnosis code No.U1100 is set in the auto A/C controller
assembly (A/C-ECU), diagnose the CAN main bus line.
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| caution |
Whenever the ECU is replaced, ensure that the communication
circuit is normal.
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The A/C-ECU receives air conditioner control-related signals from the engine-ECU
via the CAN bus lines. If the ECU cannot receive any of the air conditioner control-related
signals from the engine-ECU, diagnosis code U1100 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 engine-ECU and the
auto A/C controller assembly (A/C-ECU), the power supply system to the engine-ECU, the engine-ECU
itself, or the auto A/C controller assembly (A/C-ECU) may be faulty.
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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 auto A/C controller assembly (A/C-ECU) and the engine-ECU, and
the power supply system to the engine-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 set 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 U1100 (past trouble) may be set to the auto A/C controller assembly
(A/C-ECU) after three minutes.
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- Damaged wiring harness or connectors
- Malfunction of the engine-ECU
- Malfunction of the auto A/C 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 engine-ECU-related diagnosis code is set.
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Q.
Is the diagnosis code set?
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Diagnose the engine-ECU. (Refer to GROUP 13A 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
set.
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- ETACS-ECU
U1100: engine-ECU-related time-out diagnosis code
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Q.
Is the diagnosis code set?
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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 reset.
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Recheck if the diagnosis code is set.
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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 set.
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Q.
Is the diagnosis code set?
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Replace the engine-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 engine-ECU and auto A/C 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 reset.
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Recheck if the diagnosis code is set.
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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 set.
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Q.
Is the diagnosis code set?
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Replace the auto A/C 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 engine-ECU and the auto A/C 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 reset.
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Recheck if the diagnosis code is set.
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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 set.
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Q.
Is the diagnosis code set?
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Return to Step 1.
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The procedure is complete.
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