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 the ECU is replaced, ensure that the CAN bus lines are normal.
^ Do not drop the G and yaw rate sensor or subject it to a shock.
^ When the G and yaw rate sensor is replaced, always perform the calibration to make ASC-ECU learn the neutral point.
^ When the hydraulic unit (integrated with ASC-ECU) is replaced, always perform the calibration of steering wheel sensor, G and yaw rate sensor, brake fluid pressure sensor, cut valve, and inlet valve.

CIRCUIT OPERATION
ASC-ECU stores the calibrated value of the G and yaw rate sensor, steering wheel sensor, and master cylinder pressure sensor.

DTC SET CONDITIONS
This diagnostic trouble code is set when the calibrated value for each sensor stored in ASC-ECU is abnormal.
^ Abnormality of G and yaw rate sensor neutral position
^ Abnormality of steering wheel sensor neutral position
^ Abnormality of master cylinder pressure sensor neutral position

PROBABLE CAUSES
^ Accidental shutdown of power supply during storing operation of calibrated value
^ 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.
Using scan tool MB991958, diagnose the CAN bus lines.
Q: Is the check result normal?
YES: Go to Step 3.
NO: Repair the CAN bus lines. (Refer to Troubleshooting Can Bus Diagnostics Table.) After repairing the CAN bus line, go to Step 2.

STEP 2. DTC recheck after repairing the CAN bus line
Q: Is DTC C123A set?
YES: Go to Step 3.
NO: The procedure is complete.

STEP 3. Check for diagnostic trouble code is set.
Check if the diagnostic trouble code is set related to the G and yaw rate sensor, steering wheel sensor, and master cylinder pressure sensor.
Q: Is any DTC set?
YES: Carry out the diagnosis for the diagnostic trouble code that is set. (Refer to Diagnostic Trouble Code Descriptions.)
NO: Go to Step 4.

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

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

STEP 6. Master cylinder pressure sensor calibration Perform calibration of the brake fluid pressure sensor.
Q: Has the calibration succeeded?
YES: Go to Step 7.
NO: Replace the hydraulic unit (incorporates in ASC-ECU). Then go to Step 8.

STEP 7. Check whether the DTC is reset.
Q: Is DTC C123A set?
YES: Replace the hydraulic unit (incorporates in ASC-ECU). 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.