C123B

DTC C123B: Prolonged operation of ASC

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 (Refer to Diagnostic trouble code diagnosis Diagnostic Trouble Code Descriptions).
^ Whenever ECU is replaced, ensure that the CAN bus lines are normal.
^ Do not drop or shock the G and yaw rate sensor.
^ When the G and yaw rate sensor is replaced, always carry out calibration to make ASC-ECU learn the neutral point.
^ When the hydraulic unit (integrated with ASC-ECU) is replaced, always carry out the calibration of the steering wheel sensor, the G and yaw rate sensor and brake fluid pressure sensor.

OPERATION
ASC-ECU controls ASC by calculating the data sent from the wheel speed sensor, the steering wheel sensor, and the G and yaw rate sensor.

DTC SET CONDITIONS
This DTC is set when ASC operates for a prolonged period.

NOTE: This DTC may be set when the vehicle runs on a slippery or rough road.

PROBABLE CAUSES
^ Steering wheel sensor malfunction
^ G and yaw rate sensor malfunction
^ Improper installation of steering wheel sensor, or G and yaw rate sensor
^ ASC-ECU malfunction
^ Different steering wheel
^ Wheel alignment not performed

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

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. (Refer to Diagnosis - CAN Bus Diagnostic Table CAN Bus Diagnostics Table.) On completion, go to Step 2.

STEP 2. DTC recheck after repairing the CAN bus line
Q: Is DTC C123B set?
YES: Go to Step 3.
NO: The procedure is complete.

STEP 3. Check the wheel speed sensor, and G and yaw rate sensor-related DTC.
Check that DTCs No.C100A, C1015, C1020, C102B, C1011, C101C, C1027, C1032, C1014, C101F, C102A, C1035, C1041, C1042, C1043, C1044, C1219, C2205, C123C, and C2204 are also set.
Q: Are DTCs C100A, C1015, C1020, C102B, C1011, C101C, C1027, C1032, C1014, C101F, C102A, C1035, C1041, C1042, C1043, C1044, C1219, C2205, C123C, and C2204 also set?
YES: Carry out the diagnosis for the DTC that is set. (Refer to Diagnostic Trouble Code Descriptions) Then go to Step 10.
NO: Go to Step 4.

STEP 4. Check of G and yaw rate sensor installation status
Check that the G and yaw rate sensor is installed correctly.
Q: Is the check result normal?
YES: After checking the G and yaw rate sensor, perform the calibration of the G and yaw rate sensor to make ASC-ECU relearn the neutral point. Then go to Step 5.
NO: Reinstall the G and yaw rate sensor correctly. Then go to Step 10.

STEP 5. Using scan tool MB991958, check the service data
Check the following service data. (Refer to Scan Tool Testing and Procedures.)
^ Item 08: Lateral G sensor
^ Item 09: G sensor
^ Item 12: Yaw rate sensor
Q: Is the check result normal?
YES: Go to Step 6.
NO: Replace the G and yaw rate sensor. Then go to Step 10.

STEP 6. Check of steering wheel sensor installation status
Check that the steering wheel sensor is installed correctly.
Q: Is the check result normal?
YES: Go to Step 7.
NO: Install the steering wheel sensor correctly. Then go to Step 7.

STEP 7. Wheel alignment check
Q: Is the check result normal?
YES: After checking the wheel alignment, perform the calibration of steering wheel sensor to make ASC-ECU relearn the neutral point. Then go to Step 8.
NO: After adjusting the wheel alignment, perform the calibration of steering wheel sensor to make ASC-ECU relearn the neutral point. Then go to Step 8.

STEP 8. Using scan tool MB991958, check the service data
Check the following service data. (Refer to Scan Tool Testing and Procedures.)
^ Item 11: Steering angle
Q: Is the check result normal?
YES: Go to Step 9.
NO: Replace the steering wheel sensor. Then go to Step 10.

STEP 9. Check whether the DTC is reset.
Q: Is DTC C123B set?
YES: Replace the hydraulic unit (ASC-ECU). Then go to Step 10.
NO: Intermittent malfunction.

STEP 10. Check whether the DTC is reset.
Q: Is DTC C123B set?
YES: Return to Step 1.
NO: The procedure is complete.