DTC C1550: ECU internal error: 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)

1. 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? 

   1. YES:  Go to  Step 3.
   2. NO:  Repair the CAN bus lines (Refer to CAN BUS DIAGNOSTICS TABLE ). On completion, go to Step 2.
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? 

   1. YES:  Go to Step 3.
   2. NO:  This diagnosis is complete.
3. 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? 

   1. YES:  Replace the electric power steering-ECU (Refer to ELECTRIC POWER STEERING CONTROL UNIT (EPS-ECU)  ). Then go to Step 4.
   2. NO:  Intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTIONS ).
4. 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? 

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