C1550

DTC C1550 ECU internal error

CAUTION:

- If there is any problem in the CAN bus lines, an incorrect DTC may be set. Prior to this diagnosis, diagnose the CAN bus lines Scan Tool Testing and Procedures ).
- Whenever ECU is replaced, ensure that the CAN bus lines are normal.

OPERATION

- Power is supplied to the electric power steering-ECU from the battery.

FUNCTION

- The CAN bus signal from the torque sensor and resolver are sent to the electric power steering-ECU for motor control.

TROUBLE JUDGMENT

Judgment 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 electric power steering-ECU stops the motor control and illuminates the electric power steering warning display, then sets the DTC C1550.

PROBABLE CAUSES

- Malfunction of CAN bus line
- Malfunction of the electric power steering-ECU

DIAGNOSIS

Required Special Tools:

- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)

STEP 1. Using scan tool MB991958, diagnose the CAN bus lines.

Use scan tool to diagnose the CAN bus lines.

Q. Is the check result normal?

YES Go to Step 3.
NO Repair the CAN bus lines CAN Bus Diagnostics Chart). On completion, go to Step 2.
STEP 2. DTC recheck after resetting CAN bus lines

(1)Erase the DTC.

(2)Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.

(3)Check if the DTC is set.

Q. Is the DTC C1550 set?

YES Go to Step 3.
NO This diagnosis is complete.
STEP 3. Check whether the DTC is reset

(1)Erase the DTC.

(2)Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.

(3)Check if the DTC is set.

Q. Is the DTC C1550 set?

YES Replace the electric power steering-ECU (Refer to Service and Repair). Then go to Step 4.
NO Intermittent malfunction How to Cope With Intermittent Malfunctions).
STEP 4. Check whether the DTC is reset.

(1)Erase the DTC.

(2)Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.

(3)Check if the DTC is set.

Q. Is the DTC C1550 set?

YES Return to Step 1.
NO This diagnosis is complete.