Code No.C1550 ECU internal error

  • 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 (Refer to GROUP 54C, CAN Bus Diagnostics Table).
  • Whenever ECU is replaced, ensure that the CAN bus lines are normal.


    Power is supplied to the EPS-ECU from the battery.


    The motor current is controlled according to the information on motor and resolver, and the information on CAN bus.


Judgement Criterion
    The system data is out of the prestored control range, and the microcomputer determines that there is an internal problem.
Fail Safe, Back Up Function
    The EPS-ECU stops the motor control and illuminates the electric power steering warning display, then sets the diagnosis code No. C1550.


  • Malfunction of CAN bus line
  • Malfunction of the EPS-ECU