GM Service Manual Online
For 1990-2009 cars only

Step

Action

Normal Result(s)

Abnormal Result(s)*

1

  1. Turn the headlamp switch to the HEAD position.
  2. Turn the headlamp dimmer switch to the LOW position.
  1. The low beam headlamps are on.
  2. The high beam headlamps are off.

Headlamps Inoperative - Low Beams

2

Turn the headlamp switch to the HIGH position.

  1. The high beam headlamps are on.
  2. The high beam indicator is on.
  3. The low beam headlamps are off.

Headlamps Inoperative - High Beams

3

  1. Turn the headlamp switch OFF.
  2. Turn the ignition to RUN.
  3. Place the transaxle in gear.
  4. Apply a bright light to the daytime running lamps (DRL) ambient light sensor.

The low beam headlamps come on at a reduced intensity in approximately 30 seconds.

Daytime Running Lamps (DRL) Inoperative, Headlamp Switch Operates Normally

4

Cover the DRL ambient light sensor with a dark cloth.

The following conditions occur in approximately 15 seconds:

  1. The low beam headlamps turn on.
  2. The exterior lamps turn on.

5

  1. Turn the ignition OFF.
  2. Apply the parking brake.
  3. Apply a bright light to the daytime running lamps (DRL) ambient light sensor.
  4. Turn the ignition to the RUN position.
    • The headlamps are off.
    • The exterior lamps are off.

Park Lamps Remain On in Daylight Conditions

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