Active Stability Control System (ASC)
DTC C123C Abnormality in G and yaw rate sensor [Abnormality in lateral G sensor and yaw rate output value
(incorrect installation)]
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 CAN Bus Line Diagnostics Flow.
- 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 G and yaw rate sensor is replaced, always carry out calibration to make ASC-ECU learn the neutral point (Refer to Active Stability Control System (ASC)).
- 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 (Refer to Active Stability Control System (ASC) , Active Stability Control System (ASC) and Active Stability Control System (ASC) ).
OPERATION
ABS-ECU monitors if the output of G and yaw rate sensor is normal or not.
DTC SET CONDITIONS
This DTC is set if any malfunction below is found:
- The output value of lateral G and yaw rate is abnormal.
- When abnormality is detected by comparing the value output of the lateral G and yaw rate with the one from the steering wheel sensor and wheel speed sensor
PROBABLE CAUSES
- Wiring harness or connector failure for the special CAN bus lines between ASC-ECU and the G and yaw rate sensor
- Improper installation of the G and yaw rate sensor
- G and yaw rate sensor malfunction
- Steering wheel sensor malfunction
- Improperly installed 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 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 2.
NO Repair the CAN bus lines CAN Bus Diagnostics Chart).
On completion, go to Step 2.
STEP 2. Using scan tool MB991958, check the DTC
Check that the DTC U0125 is set in ASC-ECU.
Q. Is DTC U0125 set?
YES Troubleshoot for the DTC (Refer to U0125). Then go to Step 3.
NO Go to Step 3.
STEP 3. DTC recheck after resetting CAN bus lines
Q. Is DTC C123C set?
YES Go to Step 4.
NO The procedure is complete.
STEP 4. Check the wheel speed sensor-related DTC.
Use scan tool to check whether the wheel speed sensor-related or steering wheel sensor-related DTC is set or not.
Q. Is the DTC set?
YES Troubleshoot for the relevant DTC (Refer to Active Stability Control System (ASC)).
NO Go to Step 5.
STEP 5. G and yaw rate sensor installation check
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, carry out calibration of the G and yaw rate sensor to make ASC-ECU relearn the neutral point (Refer to Active Stability Control System (ASC)). Then go to Step 6.
NO Reinstall the G and yaw rate sensor correctly (Refer to Service and Repair), and then go to Step 12.
STEP 6. Using scan tool MB991958, check the data list
Check the following data list (Refer to Data List Reference Table).
- Item 08: Lateral G-sensor
- Item 12: Yaw rate sensor
Q. Is the check result normal?
YES Go to Step 9.
NO Go to Step 7.
STEP 7. Connector check: A-51 ASC-ECU connector, C-137 G and yaw rate sensor connector
Q. Is the check result normal?
YES Go to Step 8.
NO Repair the connector, and then go to Step 13.
STEP 8. Wiring harness check between A-51 ASC-ECU connector terminal No. 18 and C-137 G and yaw rate sensor connector terminal No. 3 as well as between A-51 ASC-ECU connector terminal No. 19 and C-137 G and yaw rate sensor connector terminal No. 2
- Check the communication circuit for open and short circuit.
Q. Is the check result normal?
YES Replace the G and yaw rate sensor (Refer to Service and Repair), and then go to Step 12.
NO Repair the wiring harness, and then go to Step 13.
STEP 9. Steering wheel sensor installation check
Check that the steering wheel sensor is installed correctly.
Q. Is the check result normal?
YES Go to Step 10.
NO Reinstall the steering wheel sensor correctly (Refer to Service and Repair), and then go to Step 10.
STEP 10. Wheel alignment check
Front Suspension.
Q. Is the check result normal?
YES After checking the wheel alignment, carry out calibration of steering wheel sensor to make ASC-ECU relearn the neutral point (Refer to Active Stability Control System (ASC)). Then go to Step 11.
NO After adjusting the wheel alignment, carry out calibration of steering wheel sensor to make ASC-ECU relearn the neutral point (Refer to Active Stability Control System (ASC)). Then go to Step 11.
STEP 11. Using scan tool MB991958, check the data list
Check the following data list (Refer to Data List Reference Table).
- Item 11: Steering angle
Q. Is the check result normal?
YES Go to Step 12.
NO Replace the steering wheel sensor (Refer to Service and Repair), and then go to Step 12.
STEP 12. Check whether the DTC is reset.
Erase the DTC.
Q. Is DTC C123C set?
YES Replace the hydraulic unit (integrated with ASC-ECU) (Refer to Active Stability Control System (ASC)), and then go to Step 13.
NO Intermittent malfunction How to Cope With Intermittent Malfunctions).
STEP 13. Check whether the DTC is reset.
Erase the DTC.
Q. Is DTC C123C set?
YES Return to Step 1.
NO The procedure is complete.