Code No. U1121: Failure information on engine-A-M/T-ECU (Related to automated manual transmission)
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- If diagnosis code No. U1121 is set in the combination meter, always diagnose the CAN bus lines.
- Whenever the ECU is replaced, ensure that the input and output signal circuits are normal.
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TROUBLE JUDGMENT
The combination meter receives allshift lever-related signal from the engine-A-M/T-ECU <Automated manual transmission> via CAN bus lines. If failure information is sent from the allshift lever-related signal, diagnosis code No. U1121 will be set.
COMMENT ON TROUBLE SYMPTOM
The M.U.T.-III shows a diagnosis code status as active.
- Connector(s), wiring harness in the CAN bus lines, the engine-A-M/T-ECU <Automated manual transmission> , allshift lever, or combination meter may be defective.
The M.U.T.-III shows a diagnosis code status as stored.
- If diagnosis code No. U1121 is stored as a past trouble, carry out diagnosis with particular emphasis on wiring and connector(s) between the engine-A-M/T-ECU <Automated manual transmission> and the allshift lever. For diagnosis procedures, refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Treat Past Trouble
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PROBABLE CAUSES
- Malfunction of the engine-A-M/T-ECU
- Malfunction of the allshift lever
- Malfunction of the combination meter
DIAGNOSIS PROCEDURE
STEP 1. M.U.T.-III CAN bus diagnostics
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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.
Q.
Is the check result normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C, Troubleshooting ). Repair the CAN bus line and go to Step 5.
STEP 2. M.U.T.-III other system diagnosis code
Check if an engine-A-M/T-ECU <Automated manual transmission> related diagnosis code is set.
Q.
Is the diagnosis code set?
Diagnose the engine-A/T-ECU <Automated manual transmission> (Refer to GROUP 22C, Troubleshooting .) And then go to Step 3.
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 set.
ETACS-ECU
- Code No. U1121: Failure information on engine-ECU or engine-A-M/T-ECU (related to engine)
Q.
Is the diagnosis code set?
Go to Step 4.
Go to Step 5.
STEP 4. Check whether the diagnosis code is reset.
Check again 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" position
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(3)On completion, check that the diagnosis code is not reset.
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Q.
Is the diagnosis code set?
Replace the engine-A-M/T-ECU <Automated manual transmission> (related to automated manual transmission).Then perform the variant coding (Refer to GROUP 00, Precautions Before Service - How to Perform Variant Coding )? After variant coding, go to Step 6.
A poor connection, open circuit or other intermittent malfunction is present in the CAN bus lines between the engine-A-M/T-ECU and the allshift lever (Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
STEP 5. Check whether the diagnosis code is reset.
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" position
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(3)On completion, check that the diagnosis code is not reset.
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Q.
Is the diagnosis code set?
Replace the combination meter. Then perform the variant coding (Refer to GROUP 00, Precautions Before Service - How to Perform Variant Coding ). After variant coding, go to Step 6.
A poor connection, open circuit or other intermittent malfunction is present in the CAN bus lines between the engine-A-M/T-ECU and the allshift lever (Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
STEP 6. Check whether the diagnosis code is reset.
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" position
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(3)On completion, check that the diagnosis code is not reset.
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Q.
Is the diagnosis code set?
Return to Step 1.
The procedure is complete.