Inspection Procedure 9

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.
- When the ASC OFF switch is pressed for 3 seconds or more, the ASC system turns OFF.
- When the ASC OFF switch is pressed and held for 15 seconds or more, ASC turns ON.

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. (Refer to Service and Repair).





(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. (Refer to Service and Repair). Then go to Step 3.

NO Replace the ASC OFF switch. (Refer to Service and Repair). 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. Harness Connector Inspection). 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. How to Cope With Intermittent Malfunctions).
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.