C1242
DTC C1242 Abnormality in G and yaw rate sensor (Abnormality in longitudinal G sensor output signal) [AWD]
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 Diagnostic trouble code diagnosis Diagnostic Trouble Code Descriptions).
^ 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. 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 (Refer to Diagnosis - CAN Bus Diagnostic Table CAN Bus Diagnostics 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?
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 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 (Refer to Diagnostic Trouble Code Descriptions).
NO: Go to Step 5.
STEP 5. Using scan tool MB991958, check the data list
Check the following service data under curb weight condition or one occupant (driver) only in the vehicle, on a flat road.(Refer to Scan Tool Testing and Procedures)
^ Item 09: G sensor
^ Item 96: G sensor offset
Q: Is the check result normal?
YES: Turn the ignition switch to the ON from OFF position. Then go to Step 9.
NO: Go to Step 6.
STEP 6. G and yaw rate sensor check
Check that the G and yaw rate sensor is installed correctly.
Q: Is the check result normal?
YES: Go to Step 7.
NO: Reinstall the G and yaw rate sensor correctly and then go to Step 10.
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.