Inspection Procedure 8: ASC OFF Display Stays ON

Inspection Procedure 8: ASC OFF Display Stays ON.





CAUTION:
^ If there is any problem in the CAN bus lines, an incorrect diagnosis code 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 to the combination meter through ETACS-ECU via CAN communication.
^ By the operation of ASC OFF switch, the ASC OFF display 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.

TECHNICAL DESCRIPTION (COMMENT)
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
^ ETACS-ECU malfunction
^ Combination meter malfunction
^ ASC-ECU malfunction
^ ASC OFF switch 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

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 9.

STEP 2. M.U.T.-III diagnostic trouble code
Use scan tool to check the diagnostic trouble code for the ASC system.
Q: Is any DTC set?
YES: Carry out the diagnosis for the diagnostic trouble code.
NO: Go to Step 3.

STEP 3. ASC OFF switch check
Q: Is the check result normal?
YES: Go to Step 4.
NO: Replace ASC OFF switch. Then go to Step 9.

STEP 4. Connector check: C-313 ETACS-ECU connector, C-32 intermediate connector, C-101 ASC OFF switch connector
Q: Is the check result normal?
YES: Go to Step 5.
NO: Repair the damaged connector.

STEP 5. Wiring harness check between C-313 ETACS-ECU connector terminal No. 15 and C-101 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 6.
NO: Repair the wiring harness between C-313 ETACS-ECU connector terminal No.15 and C-101 ASC OFF switch connector terminal No.1.

STEP 6. M.U.T.-III other system diagnostic trouble code
Using scan tool, check that the diagnostic trouble code U0141 is not set by the combination meter system.
Q: Is any DTC set?
YES: Diagnose the combination meter. Then go to Step 9.
NO: Go to Step 7.

STEP 7. M.U.T.-III other system diagnostic trouble code
Using scan tool, check that the diagnostic trouble code U0121 is not set by the ETACS system.
Q: Is any DTC set?
YES: Perform troubleshooting on ETACS-ECU. Then go to Step 8.
NO: Go to Step 8.

STEP 8. Retest the system.
Q: Does the ASC OFF display turn ON and OFF normally?
YES: Intermittent malfunction.
NO: Replace the ASC-ECU Then go to Step 9.

STEP 9. Retest the system.
Q: Does the ASC OFF display turn ON and OFF normally?
YES: The procedure is complete.
NO: Return to Step 1.