Active Skid Control System (ASC)

DTC C123C: Abnormality in G and yaw rate sensor (lateral G or yaw rate)

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.
^ When the steering wheel sensor is replaced, always perform calibration to make ASC-ECU learn the neutral point.
^ 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 supplies power to the G and yaw rate sensor at the terminal No. 1.
^ The G and yaw rate sensor outputs the signal to ASC-ECU via the special CAN bus lines.

DTC SET CONDITIONS
This diagnostic trouble code is set if any malfunction below is found:
^ Lateral G value or yaw rate value output from G and yaw rate sensor is abnormal.
^ This diagnostic trouble code is set when ASC-ECU determines that an abnormality is present by comparing the lateral G value and yaw rate values output from G and yaw rate sensor with the wheel speed value output from wheel speed sensor, and with the steering wheel angle output from steering wheel sensor.

PROBABLE CAUSES
^ Improper installation of the G and yaw rate sensor
^ G and yaw rate sensor malfunction
^ Steering wheel sensor malfunction
^ Improper installation of steering wheel sensor
^ Malfunction of wheel speed 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

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 2.
NO: Repair the CAN bus lines. After repairing the CAN bus line, go to Step 2.

STEP 2. Check for diagnostic trouble codes of other systems
Check if diagnostic trouble code No. U0125 is also set in ASC-ECU.

Q: Is DTC U0125 set?
YES: Perform troubleshooting for the diagnostic trouble code that is set. Then go to Step 3.
NO: Go to Step 3.

STEP 3. Check whether the DTC is reset.

Q: Is DTC C123C set?
YES: Go to Step 4.
NO: The procedure is complete.

STEP 4. Check of wheel speed sensor-related diagnostic trouble code
Using scan tool MB991958, check if the wheel speed sensor-related or steering wheel sensor-related diagnostic trouble code is set.

Q: Is any DTC set?
YES: Perform troubleshooting for the diagnostic trouble code that is set.
NO: Go to Step 5.

STEP 5. 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 6.
NO: Reinstall the G and yaw rate sensor correctly. Then go to Step 10.

STEP 6. Scan tool service data
Check the following service data.
^ Item 08: Lateral G-sensor
^ Item 12: Yaw rate sensor

Q: Is the check result normal?
YES: Go to Step 7.
NO: Replace the G and yaw rate sensor. Then go to Step 10.

STEP 7. 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 8.
NO: Install the steering wheel sensor correctly. Then go to Step 8.

STEP 8. 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 9.
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 9.

STEP 9. Scan tool service data
Check the following service data.
^ Item 11: Steering angle sensor

Q: Is the check result normal?
YES: Go to Step 10.
NO: Replace the steering wheel sensor. Then go to Step 10.

STEP 10. Check whether the DTC is reset.

Q: Is DTC C123C set?
YES: Replace the hydraulic unit (incorporates in ASC-ECU). Then go to Step 11.
NO: Intermittent malfunction.

STEP 11. Check whether the DTC is reset.

Q: Is DTC C123C set?
YES: Return to Step 1.
NO: The procedure is complete.