Inspection Procedure 9: When the ASC Off Switch Is Push on, ASC Does Not Be Cancelled

INSPECTION PROCEDURE 9: When the ASC OFF Switch is Push On, ASC does not be Cancelled.











CIRCUIT OPERATION
TCL/ASC-ECU terminal 38 is grounded every time the ASC OFF switch is pressed. TCL/ASC-ECU monitors this operation state and turns the ASC ON or OFF.

COMMENT
The cause is probably an open-circuit in the ASC OFF switch circuit.

TROUBLESHOOTING HINTS
^ Malfunction of the ASC OFF switch
^ Damaged harness, connector
^ Malfunction of the TCL/ASC-ECU

DIAGNOSIS

Required Special Tools:
^ MB991223: Harness Set
^ MB991997: ASC Check Harness
^ MB992006: Extra Fine Probe

STEP 1. Measure the voltage at TCL/ASC-ECU connector A-38.





1) Disconnect the TCL/ASC-ECU connector A-38.
2) Connect special tool MB991997 between the TCL/ASC-ECU and the body-side harness connector A-38.
3) Turn the ignition switch to the "ON" position.
4) Measure the voltage between special tool MB991997 connector terminal 38 (TCL/ASC-ECU connector A-38 terminal 38) and ground.
^ When the ASC OFF switch is not pressed, the voltage should measure battery positive voltage (approximately 12 volts).
^ When the ASC OFF switch is pressed, the voltage should measure 1 volt or less.
5) Turn the ignition switch to the "LOCK" (OFF) position.
6) Disconnect special tool MB991997 between the TCL/ASC-ECU and the body-side harness connector A-38.
7) Connect the TCL/ASC-ECU connector A-38.
Q: Is the voltage battery positive voltage when the ASC OFF switch is not pressed, and is the terminal voltage 1 volt or less when the ASC OFF switch is pressed?
YES: Go to Step 6.
NO: Go to Step 2.

STEP 2. Check the ASC OFF switch.

1) Remove the ASC OFF switch.





2) Connect an ohmmeter to the ASC OFF switch between terminals 1 and 2.
3) Check for continuity between terminals 1 and 2 when the ASC OFF switch is operated.
^ There is no continuity between terminals 1 and 2 when the ASC OFF switch is not pressed.
^ There is continuity between terminals 1 and 2 when the ASC OFF switch is pressed.
Q: Is there no continuity between terminals 1 and 2 when the ASC OFF switch is not pressed, and is there continuity when the ASC OFF switch is pressed?
YES: Install the ASC OFF switch. Then go to Step 3.
NO: Replace the ASC OFF switch. Then go to Step 7.

STEP 3. Check TCL/ASC-ECU connector A-38, intermediate connector C-24 and ASC OFF switch connectors C-133 for loose, corroded or damaged terminals, or terminals pushed back in the connector.





Q: Are there connectors and terminals in good condition?
YES: Go to Step 4.
NO: Repair or replace the faulty connector. Then go to Step 7.





STEP 4. Check the harness wire between TCL/ASC-ECU connector A-38 terminal 38 and ASC OFF switch connector C-133 terminal 1 for open circuit.





Q: Are there harness wires in good condition?
YES: Go to Step 5.
NO: Repair the damaged harness wire. Then go to Step 7.





STEP 5. Check the harness wire between ASC OFF switch connector C-133 terminal 2 and ground for open circuit.





Q: Is the harness wire in good condition?
YES: Go to Step 6.
NO: Repair the damaged harness wire. Then go to Step 7.





STEP 6. Retest the system
Q: Is ASC cancelled when the ASC OFF switch is push on?
YES: It can be assumed that this malfunction is intermittent.
NO: Replace the hydraulic unit (integrated with TCL/ASC-ECU). Then go to Step 7.

STEP 7. Retest the system
Q: Is ASC cancelled when the ASC OFF switch is push on for 3 seconds or longer?
YES: The procedure is complete.
NO: Return to Step 1.