Code No. C1786: Received limp Home from T/M-ECU

  • If there is any problem in the CAN bus lines, an incorrect diagnosis code may be stored. Prior to this diagnosis, diagnose the CAN bus lines.
  • Whenever the ECU is replaced, ensure that the CAN bus lines are normal.


ACC/FCM-ECU communicates with the CVT-ECU, A/T-ECU via the CAN bus lines.


This diagnosis code is stored when the abnormality below is detected:



STEP 1. Using M.U.T.-III, diagnose the CAN bus line.

Use M.U.T.-III to perform the CAN bus diagnosis.

Q. Is the check result normal?

Go to Step 2.
Repair the CAN bus lines (Refer to GROUP 54C - Troubleshooting ).

STEP 2. Use M.U.T.-III to confirm a diagnosis code of other systems.

Check the CVT diagnosis code (Refer to GROUP 23A -Troubleshooting ) or the automatic transmission (FF) diagnosis code (Refer to GROUP 23C -Troubleshooting ).

Q. Is the diagnosis code stored?

Perform the relevant troubleshooting.
Go to Step 3.

STEP 3. Check the data list.

Using M.U.T.-III, check the data list (Refer to data list reference table ).

  • Item 56: transmission fail switch

Q. Is the check result normal?

Go to Step 4.
Go to Step 4.

STEP 4. Check whether the diagnosis code is stored again.

Q. Is diagnosis code No.C1786 stored?

Replace the ACC/FCM-ECU (Refer to ).
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).