GM Service Manual Online
For 1990-2009 cars only

Step

Action

Normal Result(s)

Abnormal Result(s)*

1

  1. Turn the ignition switch to the OFF position.
  2. Place the headlamp switch in the OFF position.

All of the exterior lamps turn off.

2

Place the headlamp switch in the PARK position.

All of the park lamps light.

Exterior Lights System Check

3

  1. Place the headlamp switch in the HEAD position.
  2. Place the headlamp dimmer switch in the LOW position.
    • All of the park lamps remain on.
    • Both of the low beam headlamps light.

Headlamps Inoperative - Low Beams

4

Place the headlamp dimmer switch in the HIGH position.

    • All of the park lamps remain on.
    • The headlamps switch from the low beams to the high beams.

Headlamps Inoperative - High Beams

5

  1. Place the headlamp dimmer switch in the LOW position.
  2. Place the headlamp switch in the OFF position.
  3. Turn the ignition switch to the RUN position.
  4. Shine a bright, incandescent light on the ambient light sensor.
  5. Place the gear selector in the DRIVE position.
    • Both of the high beam headlamps light at reduced intensity.
    • All of the park lamps turn off.

Daytime Running Lamps (DRL) Headlamps Inoperative

6

  1. Place the gear selector in the PARK position.
  2. Slide the twilight sentinel switch to the MIN position.
  3. Cover the ambient light sensor.

Both of the low beam headlamps light at full intensity and park lamps turn on within 30 seconds.

Twilight Sentinel Inoperative

7

  1. Slide the twilight sentinel switch to the MAX position.
  2. Turn the ignition switch to the OFF position.

All of the exterior lamps turn off after approximately 3 minutes.

Twilight Sentinel Inoperative

* Refer to the appropriate symptom diagnostic table for the applicable abnormal result.