Code No.U1120: Engine-related CAN communication failure information
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If diagnosis code No. U1120 is set in the A/C-ECU, diagnose the CAN main bus line.
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The A/C-ECU receives vehicle speed signal from the engine-ECU <M/T> or the engine-A/T-ECU <A/T> via CAN bus lines. If failure information is sent to the vehicle speed signal, diagnosis code U1120 will be set.
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COMMENTS ON TROUBLE SYMPTOM
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Current trouble
- The vehicle speed sensor, A/C-ECU, engine-ECU <M/T> or 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 between the engine-ECU <M/T> or engine-A/T-ECU <A/T> and the vehicle speed sensor. For diagnosis procedures, refer to "How to treat past trouble" (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points
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- Damaged harness wires and connectors
- Malfunction of the engine-A/T-ECU
- 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 .) 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-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
U1120: Diagnosis code of engine-related failure information
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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. M.U.T.-III diagnosis code
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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 between the engine-ECU <M/T> or the engine-A/T-ECU <A/T> and the vehicle speed sensor. (Refer to GROUP 00, How to Cope with Intermittent Malfunction .)
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STEP 5. M.U.T.-III diagnosis code
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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 between the engine-A/T-ECU <A/T> and the vehicle speed sensor. (Refer to GROUP 00, How to Cope with Intermittent Malfunction .)
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STEP 6. M.U.T.-III diagnosis code
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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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