DTC C123B: Prolonged operation of ASC

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.
When the steering wheel sensor is replaced or re-installed, always perform the calibration to make ASC-ECU learn the neutral point. (Refer to .)
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 controls ASC by calculating the data sent from the wheel speed sensor, steering wheel sensor, and G and yaw rate sensor.

DTC SET CONDITIONS

This diagnostic trouble code is set when ASC control is operated for a prolonged period.

note

This diagnostic trouble code may be set when the vehicle runs on a slippery or rough road, or when the vehicle performs a steady state cornering.

PROBABLE CAUSES

Steering wheel sensor malfunction
G and yaw rate sensor malfunction
Improper installation of steering wheel sensor or G and yaw rate sensor
ASC-ECU malfunction
Different steering wheel
Wheel alignment not performed

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 C123B set?

	Go to Step 3.

	This diagnosis is complete.

STEP 3. Scan tool diagnostic trouble code

Check that DTCs C100A, C1015, C1020, C102B, C1011, C101C, C1027, C1032, C1014, C101F, C102A, C1035, C1041, C1042, C1043, C1044, C1219, C2205, C123C, and C2204 are also set.

Q. Are DTCs C100A, C1015, C1020, C102B, C1011, C101C, C1027, C1032, C1014, C101F, C102A, C1035, C1041, C1042, C1043, C1044, C1219, C2205, C123C, and C2204 also set?

	Carry out the diagnosis for the diagnostic trouble code that is set. (Refer to .) Then go to Step 10.

	Go to Step 4.

STEP 4. Check of G and yaw rate sensor installation status

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, perform the calibration of the G and yaw rate sensor to make ASC-ECU relearn the neutral point.(Refer to .) Then go to Step 5.

	Reinstall the G and yaw rate sensor correctly. (Refer to .) Then go to Step 10.

STEP 5. Scan tool service data

Check the following service data. (Refer to

Item 08: Lateral G sensor
Item 09: G sensor
Item 12: Yaw rate sensor

Q. Is the check result normal?

	Go to Step 6.

	Replace the G and yaw rate sensor. (Refer to .) Then go to Step 10.

STEP 6. Check of steering wheel sensor installation status

Check that the steering wheel sensor is installed correctly.

Q. Is the check result normal?

	Go to Step 7.

	Install the steering wheel sensor correctly. (Refer to .) Then go to Step 7.

STEP 7. Wheel alignment check

Refer to GROUP 33 - On-vehicles service

Q. Is the check result normal?

	After checking the wheel alignment, perform the calibration of steering wheel sensor to make ASC-ECU relearn the neutral point. (Refer to .) Then go to Step 8.

	After adjusting the wheel alignment, perform the calibration of steering wheel sensor to make ASC-ECU relearn the neutral point. (Refer to .) Then go to Step 8.

STEP 8. Scan tool service data

Check the following service data. (Refer to

Item 11: Steering angle

Q. Is the check result normal?

	Go to Step 9.

	Replace the steering wheel sensor. (Refer to .) 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. Does ASC unnecessary activation occur or is the DTC C123B set?

	Replace the hydraulic unit (incorporates in ASC-ECU). (Refer to .) 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. Does ASC unnecessary activation occur or is the DTC C123B set?

	Return to Step 1.

	The procedure is complete.