Active Stability Control System (ASC)

DTC C1242: Abnormality in G and yaw rate sensor (longitudinal G sensor)

















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 Initial Inspection and Diagnostic Overview ).
- 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 (Refer to G and Yaw Rate Sensor Calibration ).
- 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 (Refer to G and Yaw Rate Sensor Calibration , Testing and Inspection , Master Cylinder Brake Fluid Pressure Sensor Calibration , and Testing and Inspection ).

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 local CAN bus lines.

DTC SET CONDITIONS

This diagnostic trouble code is set when an abnormality is detected by a comparison of the longitudinal G value output from G and yaw rate sensor with the wheel speed value output from wheel speed sensor.

PROBABLE CAUSES

- Improper installation of the G and yaw rate sensor
- G and yaw rate sensor malfunction
- Wheel speed sensor malfunction
- ASC-ECU malfunction
- External noise interference

NOTE:
This DTC may be set also when the vehicle is driven on the four-wheel drum tester.

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 2.
NO Repair the CAN bus lines CAN Bus Diagnostics Chart).
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 (Refer to U0125).
Then go to Step 3.
NO Go to Step 3.
STEP 3. Check whether the DTC is reset.

Q. Is DTC C1242 set?

YES Go to Step 4.
NO This diagnosis is complete.
STEP 4. Check of wheel speed sensor-related diagnostic trouble code

Using scan tool MB991958, check if the wheel speed sensor-related diagnostic trouble code is set (Refer to Active Stability Control System (ASC)).

Q. Is any DTC set?

YES Perform troubleshooting for the diagnostic trouble code that is set (Refer to Active Stability Control System (ASC)).
NO Go to Step 5.
STEP 5. G and yaw rate sensor 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, perform the calibration of the G and yaw rate sensor to make ASC-ECU relearn the neutral point (Refer to G and Yaw Rate Sensor Calibration).
Then go to Step 6.
NO Reinstall the G and yaw rate sensor correctly (Refer to Service and Repair).
Then go to Step 10.
STEP 6. Scan tool data list

Check the following data list (Refer to Data List Reference Table).

- Item 09: G sensor
- Item 96: G sensor offset

Q. Is the check result normal?

YES Go to Step 9.
NO Replace the G and yaw rate sensor (Refer to Service and Repair).
Then go to Step 7.
STEP 7. Connector check: A-05 ASC-ECU connector, C-46 AWC-ECU connector, C-47 intermediate connector

Q. Is the check result normal?

YES Go to Step 8.
NO Repair the connector, and then go to Step 10.
STEP 8. Wiring harness check between A-05 ASC-ECU connector terminal No. 18 and C-38 G and yaw rate sensor connector terminal No. 3, between A-05 ASC-ECU connector terminal No. 19 and C-38 G and yaw rate sensor connector terminal No. 2, between C-46 AWC-ECU connector terminal No. 9 and C-38 G and yaw rate sensor connector terminal No. 3, between C-46 AWC-ECU connector terminal No. 10 and C-38 G and yaw rate sensor connector terminal No. 2

- Open or short circuit check of communication circuit


Q. Is the check result normal?

YES Replace the G and yaw rate sensor (Refer to Service and Repair).
Then go to Step 9.
NO Repair the wiring harness, and then go to Step 10.
STEP 9. Check whether the DTC is reset.

(1)Erase the DTC.

(2)Drive the vehicle at 12mph (20 km/h) or higher.

Q. Is DTC C1242 set?

YES Replace the hydraulic unit (integrated with ASC-ECU) (Refer to Service and Repair).
Then go to Step 10.
NO Intermittent malfunction How to Cope With Intermittent Malfunctions).
STEP 10. Check whether the DTC is reset.

(1)Erase the DTC.

(2)Drive the vehicle at 12mph (20 km/h) or higher.

Q. Is DTC C1242 set?

YES Return to Step 1.
NO The procedure is complete.