C123A

DTC C123A: Abnormality in sensor calibration

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 steering wheel sensor is replaced, always carry out calibration to make ASC-ECU learn the neutral point.
^ 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 stores the calibrated value of the G and yaw rate sensor, steering wheel sensor, and brake fluid pressure sensor.

DTC SET CONDITIONS
This DTC is set when the calibrated value for each sensor stored in ASC-ECU is not within the predetermined range.
^ Abnormality in neutral position of the G and yaw rate sensor
^ Abnormality in neutral position of the steering wheel sensor
^ Abnormality in neutral position of the brake fluid pressure sensor

PROBABLE CAUSES
^ Improper installation of G and yaw rate sensor or steering wheel sensor
^ ASC-ECU malfunction
^ External noise interference

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 resetting CAN bus lines
Q: Is DTC C123A set?
YES: Go to Step 3.
NO: The procedure is complete.

STEP 3. Check other DTC is set.
Check if the DTC related to the G and yaw rate sensor and the steering wheel sensor is set.
Q: Is any DTC set?
YES: Perform the diagnosis for the relevant DTC (Refer to Diagnostic Trouble Code Descriptions.)
NO: Go to Step 4.

STEP 4. G and yaw rate sensor calibration
Perform the calibration of G and yaw rate sensor.
Q: Has the calibration succeeded?
YES: Go to Step 5.
NO: Replace the hydraulic unit (ASC-ECU), and then go to Step 8.

STEP 5. Steering wheel sensor calibration
Perform the calibration of steering wheel sensor.
Q: Has the calibration succeeded?
YES: Go to Step 6.
NO: Replace the hydraulic unit (ASC-ECU), and then go to Step 8.

STEP 6. Brake fluid pressure sensor calibration
Perform the calibration of brake fluid pressure sensor.
Q: Has the calibration succeeded?
YES: Go to Step 7.
NO: Replace the hydraulic unit (ASC-ECU), and then go to Step 8.

STEP 7. Check whether the DTC is reset.
Q: Is DTC C123A set?
NO: Replace the hydraulic unit (ASC-ECU), and then go to Step 8.
NO: Intermittent malfunction.

STEP 8. Check whether the DTC is reset.
Q: Is DTC C123A set?
YES: Return to Step 1.
NO: The procedure is complete.