GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Headlamp Switch Igniton Supply

1

1

1

--

Headlamp Leveling Actuator Igniton Supply

1

1

1

--

Headlamp Leveling Actuator Control

1

1

1

--

Headlamp Leveling Actuator Ground

1

1

1

--

Headlamp Switch Ground

--

1

--

--

1. Headlamp Leveling Actuator Malfunction

Circuit/System Description

With the ignition in the ignition ON or ignition RUN position, voltage is supplied through the IGN E fuse. It then is dispersed to the headlamp switch and the left and right headlamp leveling actuators. The headlamp leveling actuators are then controlled by the headlamp switch to reach the desired position. The headlamp switch is permanently grounded at G201. The left headlamp leveling actuator is permanently grounded at G107 and the right headlamp leveling actuator is permanently grounded at G103.

Reference Information

Schematic Reference

Headlight Leveling Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

Headlamp Leveling Actuator Malfunction

  1. Ignition OFF, disconnect the harness connectors at the headlamp switch.
  2. Test for less than 5.0 ohms between the ground circuit terminal C X1 and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, verify that a test lamp illuminates between the headlamp switch ignition circuit terminal G X2 and ground.
  5. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  6. Reconnect the harness connectors at the headlamp switch.
  7. Disconnect the harness connector at the inoperative headlamp leveling actuator.
  8. Test for less than 5.0 ohms between the ground circuit terminal 1 and ground.
  9. If greater than the specified range, test the ground circuit for an open/high resistance.
  10. Ignition ON, verify that a test lamp illuminates between the headlamp leveling actuator ignition circuit terminal 3 and ground.
  11. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  12. Ignition ON, test for 2.0 - 8.0 volts between the headlamp leveling actuator signal circuit terminal 2 and ground while operating the leveling switch from the lowest to highest setting.
  13. If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the headlamp switch.
    If greater than the specified range, test the signal circuit for a short to voltage. if the circuit tests normal, replace the headlamp switch.
  14. If all circuits test normal, test or replace the inoperative headlamp leveling actuator.

Repair Instructions

Perform the after completing the diagnostic procedure.

    •  Headlamp Aiming
    •  Headlamp Switch Replacement
    •  Headlamp Replacement