Inspection Procedure 7: the ASC Off Display Remains Illuminated After the Engine Is Started.

Inspection Procedure 7: The ASC OFF display remains illuminated after the engine is started.














CAUTION:
^ Whenever the ECU is replaced, ensure that the CAN bus lines are normal.
^ 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.

SYSTEM 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 shortly, the ASC system is turned OFF.

TECHNICAL DESCRIPTION (COMMENT)
In the case of this trouble symptom, there may be a short circuit to the ASC OFF switch circuit.

PROBABLE CAUSES
^ Damaged wiring harness and connectors
^ ASC OFF switch malfunction
^ ETACS-ECU malfunction
^ 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. Using scan tool MB991958, diagnose the CAN bus lines.
Using scan tool MB991958, diagnose the CAN bus lines.
Q: Is the check result normal?
YES: Go to Step 2.
NO: Repair the CAN bus lines. (Refer to Troubleshooting Can Bus Diagnostics Table.) Then go to Step 9.

STEP 2. Scan tool diagnostic trouble code
Using scan tool, check the diagnostic trouble code for ASC system.
Q: Is any DTC set?
YES: Carry out the diagnosis for the DTC. (Refer to Diagnostic Trouble Code Descriptions.)
NO: Go to Step 3.

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

STEP 4. Connector check: C-313 ETACS-ECU connector, C-42 intermediate connector, C-135 ASC OFF switch connector
Q: Is the check result normal?
YES: Go to Step 5.
NO: Repair the defective connector.

STEP 5. Wiring harness check between C-313 ETACS-ECU connector terminal No. 15 and C-135 ASC OFF switch connector terminal No. 1
^ Short circuit check of the signal line 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-119 ASC OFF switch connector terminal No. 1.

STEP 6. Scan tool diagnostic trouble code for other system
Using scan tool MB991958, check if diagnostic trouble code No. U0141 is set by the combination meter system.
Q: Is the DTC set?
YES: Diagnose the combination meter. (Refer to Combination Meter, Troubleshooting Combination Meter.) Then go to Step 9.
NO: Go to Step 7.

STEP 7. Scan tool diagnostic trouble code for other system
Using scan tool MB991958, check if diagnostic trouble code No. U0121 is set by ETACS system.
Q: Is the DTC set?
YES: Diagnose the ETACS-ECU (Refer to ETACS, Troubleshooting ETACS.) 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 hydraulic unit (incorporates in 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.