DTC C123A: Abnormality in sensor calibration

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 steering wheel sensor is replaced, always carry out calibration to make ASC-ECU learn the neutral point (Refer to ).
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

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

DTC SET CONDITIONS

This DTC is set when the calibrated value for each sensor stored in ASC-ECU is not within the predetermined range.

Abnormality in neutral position of the G and yaw rate sensor
Abnormality in neutral position of the steering wheel sensor
Abnormality in neutral position of the brake fluid pressure sensor

PROBABLE CAUSES

Improper installation of G and yaw rate sensor or steering wheel sensor
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. M.U.T.-III CAN bus diagnostics

Use scan tool to diagnose the CAN bus lines.

Q. Is the check result normal?

	Go to Step 3.

	Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostic table ). On completion, go to Step 2.

STEP 2. DTC recheck after resetting CAN bus lines

Q. Is DTC C123A set?

	Go to Step 3.

	The procedure is complete.

STEP 3. Check other DTC is set.

Check if the DTC related to the G and yaw rate sensor and the steering wheel sensor is set.

Q. Is any DTC set?

	Go to Step 4.

	Perform the diagnosis for the relevant DTC (Refer to .)

STEP 4. G and yaw rate sensor calibration

Perform calibration of G and yaw rate sensor (Refer to

Q. Has the calibration succeeded?

	Go to Step 5.

	Replace the hydraulic unit (ASC-ECU) (Refer to ), and then go to Step 8.

STEP 5. Steering wheel sensor calibration

Perform calibration of steering wheel sensor (Refer to

Q. Has the calibration succeeded?

	Go to Step 6.

	Replace the hydraulic unit (ASC-ECU) (Refer to ), and then go to Step 8.

STEP 6. Brake fluid pressure sensor calibration

Perform calibration of brake fluid pressure sensor (Refer to

Q. Has the calibration succeeded?

	Go to Step 7.

	Replace the hydraulic unit (ASC-ECU) (Refer to ), and then go to Step 8.

STEP 7. Check whether the DTC is reset.

Q. Is DTC C123A set?

	Replace the hydraulic unit (ASC-ECU) (Refer to ), and 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.