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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 (Refer to GROUP 54C - Diagnostic trouble code diagnosis ).
  • 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 ).
  • 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 , and ).

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?
Go to Step 2.
Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostic table ). 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?
Troubleshoot for the DTC (Refer to ). Then go to Step 3.
Go to Step 3.

STEP 3. DTC recheck after resetting CAN bus lines

Q. Is DTC C123C set?
Go to Step 4.
The procedure is complete.

STEP 4. Check the wheel speed sensor-related or steering wheel 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?
Troubleshoot for the relevant DTC (Refer to ).
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?
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 .) Then go to Step 6.
Reinstall the G and yaw rate sensor correctly (Refer to ), and then go to Step 12.

STEP 6. Using scan tool MB991958, check the data list
Check the following service data (Refer to ).

  • Item 08: Lateral G-sensor
  • Item 12: Yaw rate sensor

Q. Is the check result normal?
Go to Step 9.
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?
Go to Step 8.
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. 2 as well as between A-51 ASC-ECU connector terminal No. 19 and C-137 G and yaw rate sensor connector terminal No. 3

  • Check the communication circuit for open and short circuit.

Q. Is the check result normal?
Replace the G and yaw rate sensor (Refer to ), and then go to Step 12.
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?
Go to Step 10.
Reinstall the steering wheel sensor correctly (Refer to ), and then go to Step 10.

STEP 10. Wheel alignment check
Refer to GROUP 33 - On-vehicles service .

Q. Is the check result normal?
After checking the wheel alignment, carry out calibration of steering wheel sensor to make ASC-ECU relearn the neutral point. (Refer to ). Then go to Step 11.
After adjusting the wheel alignment, carry out calibration of steering wheel sensor to make ASC-ECU relearn the neutral point (Refer to ). Then go to Step 11.

STEP 11. Using scan tool MB991958, check the data list
Check the following service data (Refer to ).

  • Item 11: Steering angle

Q. Is the check result normal?
Go to Step 12.
Replace the steering wheel sensor (Refer to ), and then go to Step 12.

STEP 12. Check whether the DTC is reset.
(1)Erase the DTC.
(2)Drive the vehicle at 12mph (20 km/h) or higher.

Q. Is DTC C123C set?
Replace the hydraulic unit (integrated with ASC-ECU) (Refer to ), and then go to Step 13.
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).

STEP 13. Check whether the DTC is reset.
(1)Erase the DTC.
(2)Drive the vehicle at 12mph (20 km/h) or higher.

Q. Is DTC C123C set?
Return to Step 1.
The procedure is complete.