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

Required Special Tools: 

• MB991223: Harness Set
• MB991997: ASC Check Harness
• MB992006: Extra Fine Probe

1. STEP 1. Measure the terminal 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 terminal 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 terminal 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.

   Fig 1: Measuring Terminal Voltage At TCL/ASC-ECU Connector A-38

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2. STEP 2. Check the ASC OFF switch. 
   1. Remove the ASC OFF switch. (Refer to 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.
        Fig 2: Checking For Continuity Between Terminals 1 And 2 When ASC OFF Switch Is Operated

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   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 ASC OFF SWITCH  ). Then go to Step 3.

   NO  : Replace the ASC OFF switch. (Refer to ASC OFF SWITCH  ). Then go to Step  7.

3. 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. (Refer to HARNESS INSPECTION and CONNECTOR INSPECTION SERVICE POINTS ). Then go to Step  7.

   Fig 3: Locating TCL/ASC-ECU Connector A-38

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   Fig 4: Locating Intermediate Connector C-24 And ASC OFF Switch Connectors C-133

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4. 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 damage. 

   Q: Are there harness wires in good condition? 

   YES  : Go to Step 5.

   NO  : Repair the damaged harness wire. Then go to Step  7.

   Fig 5: Locating TCL/ASC-ECU Connector A-38

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   Fig 6: Locating ASC OFF Switch Connector C-133

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

   Q: Is the harness wire in good condition? 

   YES  : Go to Step 6.

   NO  : Repair the damaged harness wire. Then go to Step  7.

   Fig 7: Locating ASC OFF Switch Connector C-133

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   Fig 8: Locating Ground Terminal

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6. 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. (Refer toHOW TO COPE WITH INTERMITTENT MALFUNCTIONS ).

   NO  : Replace the hydraulic unit (integrated with TCL/ASC-ECU). (Refer to HYDRAULIC UNIT ). Then go to Step 7.

7. STEP 7. Retest the system 

   Q: Is ASC cancelled when the ASC OFF switch is push on? 

   YES  : The procedure is complete.

   NO  : Return to Step  1.