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 set. 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 set when the abnormality below is detected:



STEP 1. M.U.T.-III CAN bus diagnostics.

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. M.U.T.-III other system diagnosis code.

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 set?

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: tansmission fail switch

Q. Is the check result normal?

Go to Step 4.
Go to Step 4.

STEP 4. Check whether the diagnosis code is reset.

Q. Is diagnosis code No.C1786 set?

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