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.
^ 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. M.U.T.-III CAN bus diagnostics
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. 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: Go to Step 4.
NO: Perform the diagnosis for the relevant DTC

STEP 4. G and yaw rate sensor calibration
Perform 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 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 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.