ASC

DTC C1242 Abnormality in G and yaw rate sensor (Abnormality in longitudinal G sensor output signal) [RALLIART]





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.
^ 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.
^ 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.

OPERATION
ABS-ECU monitors if the output of G and yaw rate sensor is normal or not.

DTC SET CONDITIONS
This DTC is set when the abnormality is detected by comparing the longitudinal G-sensor value output from the G and yaw rate sensor with the value output from the 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
^ Malfunction of wheel speed sensor
^ ASC-ECU malfunction
^ External noise interference

NOTE: When rotated on the four-wheel drum tester, this DTC may be set.

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. M.U.T.-III CAN bus diagnosis
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. On completion, go to Step 2.

STEP 2. M.U.T.-III DTC
Check that the DTC U0125 is set in ASC-ECU.

Q: Is DTC U0125 set?
YES: Troubleshoot for the DTC. Then go to Step 3.
NO: Go to Step 3.

STEP 3. DTC recheck after resetting CAN bus lines

Q: Is DTC C1242 set?
YES: Go to Step 4.
NO: The procedure is complete.

STEP 4. Check the wheel speed sensor-related DTC.
Use the scan tool to check whether the wheel speed sensor-related DTC is set or not.

Q: Is the DTC set?
YES: Troubleshoot for the relevant DTC.
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, carry out 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, and then go to Step 10.

STEP 6. M.U.T.-III data list
Check the following service data.
^ Item 09: G 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 10.

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?
YES: Replace the G and yaw rate sensor. Then go to Step 9.
NO: Repair the wiring harness, and then go to Step 10.

STEP 9. Check whether the DTC is reset.

Q: Is DTC C1242 set?
YES: Replace the hydraulic unit (ASC-ECU), and then go to Step 10.
NO: Intermittent malfunction.

STEP 10. Check whether the DTC is reset.

Q: Is DTC C1242 set?
YES: Return to Step 1.
NO: The procedure is complete.