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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The A/C-ECU receives engine control related signals from the engine-ECU <M/T> or the engine automated manual transmission electronic control unit (Engine-A-M/T-ECU) <Automated manual transmission> through CAN bus lines. If the ECU can receive none of these signals, diagnosis code U1100 will be set.
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COMMENTS ON TROUBLE SYMPTOM
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The M.U.T.-III shows a diagnosis code status as active.
- The followings are suspected; wiring harness or connector(s) in the CAN bus lines between the engine-ECU <M/T> or the engine-A-M/T-ECU <Automated manual transmission> and the A/C-ECU, power supply to the engine-ECU <M/T> or the engine-A-M/T-ECU <Automated manual transmission>, or the A/C-ECU, the engine-ECU <M/T>, the engine-A-M/T-ECU <Automated manual transmission>.
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The M.U.T.-III shows a diagnosis code status as stored.
- Carry out diagnosis with particular emphasis on wiring harness or connector(s) in the CAN bus lines between the engine-ECU <M/T> or the engine-A-M/T-ECU <Automated manual transmission> and the A/C-ECU, power supply to the engine-ECU <M/T> or the engine-A-M/T-ECU <Automated manual transmission>,. For diagnosis procedures, refer to "How to cope with past trouble" (Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to cope with past trouble
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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 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 54C - Explanation about the M.U.T.-III CAN bus diagnostics ).
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If the ignition switch is turned on without starting the engine and then three minutes passes, the A/C-ECU may store U1100 and U1101 as past trouble.
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- Damaged wiring harness or connectors
- Malfunction of the engine-ECU <M/T> or the engine-A-M/T-ECU <Automated manual transmission>
- Malfunction of the A/C-ECU
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STEP 1. M.U.T.-III CAN bus diagnostics
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| warning |
Since the radiator fan rotates during CAN bus line diagnostics, make sure that no one is servicing the engine compartment before diagnosing the CAN bus line. Since the CAN communication stops when diagnosing the CAN bus line, the ETACS-ECU detects the time-out of the engine-ECU, and activates the radiator fan to prevent overheating as fail-safe.
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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 line (Refer to GROUP 54C - 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 that the engine control system sets a diagnosis code.
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Q.
Is the diagnosis code set?
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Diagnose the engine control system. Refer to GROUP 13A - Troubleshooting . <134> Refer to GROUP 13B - Troubleshooting . <135> Refer to GROUP 13C - Troubleshooting . <4G1>
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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
- ETACS
U1100 or U1101: Engine control 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) position 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-M/T-ECU <Automated manual transmission>, 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-M/T-ECU <Automated manual transmission> 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) position 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-M/T-ECU <Automated manual transmission> 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) position 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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