Inspection Procedure 8: ASC Off Display or ASC Off Light Stays on After the Engine Is Started

Inspection Procedure 8: ASC OFF Display or ASC OFF Light Stays ON after the Engine is Started.





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.
^ Whenever ECU is replaced, ensure that the CAN bus lines are normal.
^ 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 sends the illumination request signal of ASC OFF display or ASC OFF light to the combination meter through ETACS-ECU via CAN communication.
^ By the operation of ASC OFF switch, the ASC OFF display or ASC OFF light illuminates when the ASC function is stopped.
^ When the ASC OFF switch is pressed for 3 seconds or more, the ASC system turns OFF.
^ When the ASC OFF switch is pressed for 15 seconds or more, the ASC is kept in ON state and the system cannot be turned OFF until the ignition switch is turned to the ON position next time.

COMMENTS ON TROUBLE SYMPTOM
This may be caused by faults in the CAN bus line, ETACS-ECU, combination meter or ASC-ECU.

PROBABLE CAUSES
^ Damaged wiring harness and connectors
^ Malfunction of ETACS-ECU
^ Combination meter malfunction
^ ASC-ECU malfunction

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?
YES: Go to Step 2.
NO: Repair the CAN bus lines. Then go to Step 10.

STEP 2. M.U.T.-III DTC
Use scan tool to check the DTC for the ASC system.

Q: Is the DTC set?
YES: Carry out the diagnosis for the DTC.
NO: Go to Step 3.

STEP 3. Actuator test of combination meter
Perform the following actuator test by the combination meter system, and check if the ASC OFF display or light illuminates normally.
^ Item No.7: Indicator 1

Q: Is the check result normal?
YES: Go to Step 4.
NO: Replace the combination meter. Then go to Step 9.

STEP 4. ASC OFF switch check

Q: Is the check result normal?
YES: Go to Step 5.
NO: Replace ASC OFF switch. Then go to Step 10.

STEP 5. Connector check: C-313 ETACS-ECU connector, C-36 intermediate connector, C-45 ASC OFF switch connector

Q: Is the check result normal?
YES: Go to Step 6.
NO: Repair the damaged connector.

STEP 6. Wiring harness check between C-313 ETACS-ECU connector terminal No.15 and C-45 ASC OFF switch connector terminal No.1
^ Check the power supply circuit for short circuit.

Q: Is the check result normal?
YES: Go to Step 7.
NO: Repair the wiring harness between C-313 ETACS-ECU connector terminal No.15 and C-45 ASC OFF switch connector terminal No.1.

STEP 7. M.U.T.-III DTC for other systems
Using scan tool, check that DTC U0141 is not set by the combination meter system.

Q: Is the DTC set?
YES: Diagnose the combination meter. Then go to Step 10.
NO: Go to Step 8.

STEP 8. M.U.T.-III DTC for other systems
Using scan tool, check that DTC U0121 is not set by the ETACS system.

Q: Is the DTC set?
YES: Perform troubleshooting on ETACS-ECU. Then go to Step 9.
NO: Go to Step 9.

STEP 9. Retest the system.

Q: Does ASC OFF display or ASC OFF light turn ON and OFF normally?
YES: Intermittent malfunction.
NO: Replace the hydraulic unit (integrated with ASC-ECU). Then go to Step 10.

STEP 10. Retest the system.

Q: Does ASC OFF display or ASC OFF light turn ON and OFF normally?
YES: The procedure is complete.
NO: Return to Step 1.