ASC

DTC C1242: Abnormality in G and yaw rate 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.
^ 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
^ 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 special CAN bus lines.

DTC SET CONDITIONS
This diagnostic trouble code 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
^ 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

STEP 1. M.U.T.-III CAN bus diagnostics
Use scan tool to diagnose the CAN bus lines.
Q: Is the check result normal?
YES: Go to Step 3.
NO: Repair the CAN bus lines. On completion, go to Step 2.

STEP 2. M.U.T.-III diagnostic trouble code
Check that the diagnostic trouble code U0125 is set in ASC-ECU.
Q: Is the diagnostic trouble code No.U0125 set?
YES: Troubleshoot for the diagnostic trouble code. Then go to Step 3.
NO: Go to Step 3.

STEP 3. Diagnostic trouble code 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 diagnostic trouble code.
Use scan tool to check whether the wheel speed sensor-related diagnostic trouble code is set or not.
Q: Is any DTC set?
YES: Troubleshoot for the relevant diagnostic trouble code.
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. Then go to Step 6.
NO: Reinstall the G and yaw rate sensor correctly, and then go to Step 8.

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 7.
NO: Replace the G and yaw rate sensor, and then go to Step 7.

STEP 7. Check whether the diagnostic trouble code is reset.
Q: Is DTC C1242 set?
YES: Replace the ASC-ECU, and then go to Step 8.
NO: Intermittent malfunction.

STEP 8. Check whether the diagnostic trouble code is reset.
Q: Is DTC C1242 set?
YES: Return to Step 1.
NO: This diagnosis is complete.