DTC C123A: Abnormality in sensor calibration

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 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 .)
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 , , , and .)

CIRCUIT OPERATION

ASC-ECU stores the calibrated value of the G and yaw rate sensor, steering wheel sensor, and master cylinder pressure sensor.

DTC SET CONDITIONS

This diagnostic trouble code is set when the calibrated value for each sensor stored in ASC-ECU is abnormal.

Abnormality of G and yaw rate sensor neutral position
Abnormality of steering wheel sensor neutral position
Abnormality of master cylinder pressure sensor neutral position

PROBABLE CAUSES

Accidental shutdown of power supply during storing operation of calibrated value
ASC-ECU malfunction
External noise interference

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?

	Go to Step 3.

	Repair the CAN bus lines. (Refer to GROUP 54C - Troubleshooting .) After repairing the CAN bus line, go to Step 2.

STEP 2. DTC recheck after repairing the CAN bus line

Q. Is DTC C123A set?

	Go to Step 3.

	The procedure is complete.

STEP 3. Check for diagnostic trouble code is set.

Check if the diagnostic trouble code is set related to the G and yaw rate sensor, steering wheel sensor, and master cylinder pressure sensor.

Q. Is any DTC set?

	Carry out the diagnosis for the diagnostic trouble code that is set. (Refer to .)

	Go to Step 4.

STEP 4. G and yaw rate sensor calibration

Perform calibration of the G and yaw rate sensor. ( Refer to

Q. Has the calibration succeeded?

	Go to Step 5.

	Replace the hydraulic unit (incorporates in ASC-ECU).(Refer to .) Then go to Step 8.

STEP 5. Steering wheel sensor calibration

Perform calibration of the steering wheel sensor. ( Refer to

Q. Has the calibration succeeded?

	Go to Step 6.

	Replace the hydraulic unit (incorporates in ASC-ECU).(Refer to .) Then go to Step 8.

STEP 6. Master cylinder pressure sensor calibration

Perform calibration of the brake fluid pressure sensor. ( Refer to

Q. Has the calibration succeeded?

	Go to Step 7.

	Replace the hydraulic unit (incorporates in ASC-ECU).(Refer to .) Then go to Step 8.

STEP 7. Check whether the DTC is reset.

Q. Is DTC C123A set?

	Replace the hydraulic unit (incorporates in ASC-ECU).(Refer to .) Then go to Step 8.

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

STEP 8. Check whether the DTC is reset.

Q. Is DTC C123A set?

	Return to Step 1.

	The procedure is complete.