Inspection Procedure 9: When the ASC Switch is Push On, ASC System does not Cancelled.




OPERATION



COMMENT



PROBABLE CAUSES



  • Malfunction of the ASC switch
  • Damaged harness, connector
  • Malfunction of the ASTC-ECU

DIAGNOSIS

STEP 1. Voltage measurement at ASTC-ECU connector A-48.

(1)Disconnect the connector A-48, and connect special tool ASC Check Harness (MB992159) to the wiring harness-side connector.
note Do not connect special tool ASC Check Harness (MB992159) to the ASTC-ECU.
(2)Turn the ignition switch to the "ON" position.
(3)Measure the terminal voltage between special tool MB992159 connector terminal 36 (ASTC-ECU connector A-48 terminal 36) and earth.
OK:
  • When the ASC switch is not pressed, the voltage should measure battery positive voltage (approximately 12 volts.)
  • When the ASC switch is pressed, the voltage should measure 1 volt or less.
(4)Turn the ignition switch to the "LOCK" (OFF) position.
(5)Disconnect special tool MB992159 between the ASTC-ECU and the body-side harness connector.
(6)Connect all the connectors from the ASTC-ECU.

Q. Is the check result normal?

Go to Step 6.

Go to Step 2.

STEP 2. Check the ASC switch.
(1)Remove the ASC switch. (Refer to .)

(2)Connect an ohmmeter to the ASC switch between terminals 1 and 2.
(3)Check for continuity between terminals 1 and 2 when the TCL switch is operated.
OK:
  • There is no continuity between terminals 1 and 2 when the ASC switch is not pressed.
  • There is continuity between terminals 1 and 2 when the ASC switch is pressed.

Q. Is the check result normal?

Install the ASC switch (Refer to .) Then go to Step 6.

Replace the ASC switch (Refer to .) Then go to Step 7.

STEP 3. Check ASTC-ECU connector A-48, intermediate connector C-54 <L.H.drive vehicles> or C-14 <R.H.drive vehicles> and ASC switch connector C-140 for loose, corroded or damaged terminals, or terminals pushed back in the connector.



Q. Is the check result normal?

Go to Step 4.

Repair or replace the faulty connector. Then go to Step 7.

STEP 4. Check the harness wire between ASTC-ECU connector A-48 terminal 36 and ASC switch connector C-140 terminal 1 for damage.



Q. Is the check result normal?

Go to Step 5.

Repair the damaged harness wire. Then go to Step 7.

STEP 5. Check the harness wire between ASC switch connector C-140 terminal 2 and earth for damage.


Q. Is the check result normal?

Go to Step 6.

Repair the damaged harness wire. Then go to Step 7.

STEP 6. Retest the system

Q. Is ASC and ATC system cancelled when the ASC switch is push on?
It can be assumed that this malfunction is intermittent. (Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Replace the hydraulic unit (integrated with ASTC-ECU). Then go to Step 7.

STEP 7. Retest the system

Q. Does ASC and ATC system cancelled, when the ASC switch is push on?
The procedure is complete.
Return to Step 1.