Diagnosis code No.12 Engine-A/T-ECU time-out (related to A/T)


caution If diagnosis code No.12 is set in the ETACS, diagnose the CAN main bus line.
caution Whenever the ECU is replaced, ensure that the communication circuit is normal.

TROUBLE JUDGMENT

  • The ETACS-ECU receives engine and transmission control-related signals from the engine-A/T-ECU via the CAN bus lines. If the ECU cannot receive the transmission control signal at all, diagnosis code No.12 will be set.
note For M/T-vehicles, diagnosis code No.12 does not mean that there is a problem.

COMMENTS ON TROUBLE SYMPTOM
Current trouble
  • Connector(s) or wiring harness in the CAN bus lines between the ETACS-ECU and the engine-A/T-ECU, the power supply system to the engine-A/T-ECU <A/T>, or the ETACS-ECU itself may be defective.
Past trouble
  • If diagnosis code No.12 is stored as a past trouble, carry out diagnosis with particular emphasis on wiring and connector(s) in the CAN bus line between the ETACS-ECU and the engine-A/T-ECU, and the power supply system to the engine-A/T-ECU <A/T>. For diagnosis procedures, refer to "How to treat past trouble" (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points ).
    note 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 Use Troubleshooting/Inspection Service Points 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 - CAN Bus Line Diagnostic Flow ).

POSSIBLE CAUSES

  • Malfunction of the engine-A/T-ECU
  • Malfunction of the ETACS-ECU
  • Malfunction of the CAN bus

DIAGNOSTIC 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 54F - Troubleshooting ). Repair the CAN bus line and go to Step 6.

Step 2. Check for A/T control-related diagnosis code.
Check if an A/T system diagnosis code is set.

Q. Is the check result normal?
Go to Step 3.
Diagnose the automatic transmission system (Refer to GROUP 23A - Troubleshooting ).

Step 3. M.U.T.-III diagnosis code
Check if a diagnosis code, which relates to CAN communication-linked systems below, is set.

  • Combination meter
    U1101: Engine-related time-out diagnosis code

Q. Is the check result normal?
Go to Step 5.
Go to Step 4.

Step 4. Check whether the diagnosis code is reset.
Check again if the diagnosis code is set.
(1)Erase the diagnosis code.
(2)Ignition switch: LOCK (OFF) position to ON
(3)On completion, check that the diagnosis code is not reset.

Q. Is the check result normal?
A poor connection, open circuit or other intermittent malfunction is present in the CAN bus lines between the engine-A/T-ECU and the ETACS-ECU (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points ).
Replace the engine-A/T-ECU, and then go to Step 6.

Step 5. Check whether the diagnosis code is reset.
Check again if the diagnosis code is set.
(1)Erase the diagnosis code.
(2)Ignition switch: LOCK (OFF) position to ON
(3)On completion, check that the diagnosis code is not reset.

Q. Is the check result normal?
A poor connection, open circuit or other intermittent malfunction is present in the CAN bus lines between the engine-A/T-ECU and the ETACS-ECU (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points ).
Replace the ETACS-ECU, and then go to Step 6.

Step 6. Check whether the diagnosis code is reset.
Recheck if the diagnosis code is set.
(1)Erase the diagnosis code.
(2)Ignition switch: LOCK (OFF) position to ON
(3)On completion, check that the diagnosis code is not reset.

Q. Is the check result normal?
The procedure is complete.
Return to Step 1.