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 (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 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?

	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. M.U.T.-III 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 C1242 set?

	Go to Step 4.

	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?

	Troubleshoot for the relevant DTC (Refer to ).

	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?

	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 10.

STEP 6. M.U.T.-III data list

Check the following service data (Refer to

Item 09: G 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 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?

	Replace the G and yaw rate sensor.(Refer to .) Then go to Step 9.

	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?

	Replace the hydraulic unit (integrated with ASC-ECU) (Refer to ), and then go to Step 10.

	Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).

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?

	Return to Step 1.

	The procedure is complete.