C123A

DTC C123A: Abnormality in sensor calibration

CAUTION:
^ If there is any problem in the CAN bus lines, an incorrect diagnostic trouble code may be set. Prior to this diagnosis, diagnose the CAN bus lines.
^ Whenever ECU is replaced, ensure that the CAN bus lines are normal.
^ When the steering wheel sensor is replaced, always carry out calibration to make ASC-ECU learn the neutral point.
^ 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.

CIRCUIT 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 diagnostic trouble code 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

PROBABLE CAUSES
^ ASC-ECU malfunction
^ External noise interference
^ Accidental shutdown of power supply during the storing operation of calibrated value

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

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. Diagnostic trouble code 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 diagnosis code is set.
Check whether the DTC related to G and yaw rate sensor and the steering wheel sensor is set.
Q: Is any diagnosis code set?
YES: Go to Step 4.
NO: Diagnose for the 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 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 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 ASC-ECU, and then go to Step 8.

STEP 7. Check whether the diagnostic trouble code is reset.
Q: Is DTC C123A set?
YES: Replace the ASC-ECU, and then go to Step 8.
NO: Intermittent malfunction.

STEP 8. Check whether the diagnostic trouble code is reset.
Q: Is DTC C123A set?
YES: Return to Step 1.
NO: This diagnosis is complete.