Code No.U1100: Engine CAN communication time-out
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If diagnosis code No. U1100 is set in the 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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U1100
- A/C-ECU receives engine control system-related signals from the engine-ECU <M/T> or the engine-A/T-ECU <A/T> via CAN bus lines. If the display unit can not receive the necessary signals, diagnosis code U1100 will be set.
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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 <M/T>, engine-A/T-ECU <A/T> and the A/C-ECU, the power supply system to the engine-A/T-ECU, the A/C-ECU, the engine-ECU <M/T> or the engine-A/T-ECU <A/T> 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 engine-ECU <M/T>, engine-A/T-ECU <A/T> and the A/C-ECU, the power supply system to the engine-ECU <M/T> or the engine-A/C-ECU <A/T>. For diagnosis procedures, refer to "How to cope with past trouble" (Refer to GROUP 00- How to Use Troubleshooting/Inspection Service Points
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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 Malfunctions 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 54F, Explanation about the M.U.T.-III CAN bus diagnostics ).
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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 A/C-ECU after three minutes.
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- Damaged harness wires and connectors
- Malfunction of engine-ECU <M/T> or engine-A/T-ECU <A/T>
- Malfunction of the 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 54F, Troubleshooting .) Repair the CAN bus line and then 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-related diagnosis code is set.
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Q.
Is the diagnosis code set?
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Diagnose the engine control system. Refer to <Except vehicles for Hong Kong and Singapore> or <Vehicles for Hong Kong and Singapore>.
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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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- Combination meter
U1100: Engine-related time-out diagnosis code
- Multi-centre display
U1100: Engine-related time-out diagnosis code
- ETACS
011 or 012: diagnosis code of engine-related time-out
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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 <M/T> or the engine-A/T-ECU <A/T>, go to Step 6.
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A poor connection, open circuit or other intermittent malfunction is present in the CAN bus lines between the engine-ECU <M/T> or the engine-A/T-ECU <A/T> and the 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 A/C-ECU, and then go to Step 6.
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A poor connection, open circuit or other intermittent malfunction is present in the CAN bus lines between the engine-ECU <M/T> or the engine-A/T-ECU <A/T> and the 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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