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.
  • Whenever the ECU is replaced, ensure that the communication circuit is normal.
note When the diagnosis codes relating to the CAN communication error are set, make sure of the vehicle equipment. When the vehicle is not equipped with the system the ETACS-ECU communicates to, the diagnosis code is always set. This is not abnormal.

TROUBLE JUDGMENT

  • The ETACS-ECU receives 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, 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. 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 54D - CAN Bus Line Diagnostic Flow ).

PROBABLE CAUSES

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

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

STEP 2. M.U.T.-III other system diagnosis code
Check if an A/T system diagnosis code is set.

Q. Is the diagnosis code set?
Diagnose the A/T system (Refer to GROUP 23A - Troubleshooting <A/T> ).
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
    U1101: Engine-related time-out diagnosis code

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 to the ETACS-ECU.
(1)Erase the diagnosis code.
(2)Ignition switch: LOCK (OFF) position to ON
(3)
caution It takes one minute until diagnosis code is detected.
On completion, check that the diagnosis code is not reset.

Q. Is the diagnosis code set?
Replace the engine-A/T-ECU, and then go to Step 6.
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 ).

STEP 5. Check whether the diagnosis code is reset.
Check again if the diagnosis code is set to the ETACS-ECU.
(1)Erase the diagnosis code.
(2)Ignition switch: LOCK (OFF) position to ON
(3)
caution It takes one minute until diagnosis code is detected.
On completion, check that the diagnosis code is not reset.

Q. Is the diagnosis code set?
Replace the ETACS-ECU, and then go to Step 6.
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 ).

STEP 6. Check whether the diagnosis code is reset.
Recheck if the diagnosis code is set to the ETACS-ECU.
(1)Erase the diagnosis code.
(2)Ignition switch: LOCK (OFF) position to ON
(3)
caution It takes one minute until diagnosis code is detected.
On completion, check that the diagnosis code is not reset.

Q. Is the diagnosis code set?
Return to Step 1.
The procedure is complete.