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 ETACS-ECU, diagnose the CAN main bus line.
- Whenever the ECU is replaced, ensure that the input and output signal circuits are normal.
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TROUBLE JUDGMENT
The ETACS-ECU receives allshift lever-related signal from the engine-A-M/T-ECU via CAN bus lines. If failure information is sent to 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, allshift lever, or ETACS-ECU 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 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 ETACS-ECU
DIAGNOSIS PROCEDURE
STEP 1. M.U.T.-III CAN bus diagnostics
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 ). On completion, go to Step 5.
STEP 2. Check the diagnosis code of the engine-A-M/T-ECU
Check if an engine-A-M/T-ECU-related diagnosis code is set.
Q.
Is the diagnosis code set?
Diagnose the engine-A-M/T-ECU (Refer to GROUP 22C - Troubleshooting ).
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.
- Combination meter
U1121: Failure information on engine-ECU <M/T> or engine-A-M/T-ECU <Automated manual transmission> (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)Turn the ignition switch from "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 (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)Turn the ignition switch from "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 ETACS-ECU. Then perform the variant coding and write the VIN data (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)Turn the ignition switch from "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.