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.

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.

3

  1. Turn the headlamp switch to the OFF position.
  2. Apply a bright incandescent light to the daytime running lamps (DRL) ambient light sensor.
  3. Turn the ignition to the RUN position.
  4. Disengage the park brake.

The high beam headlamps come ON at a reduced intensity in approximately 30 seconds.

4

Cover the DRL ambient light sensor with a dark cloth.

The following conditions occur in approximately 15 seconds:

  1. The high beam headlamps turn OFF.
  2. The low beam headlamps turn ON.
  3. The exterior lamps turn ON.

5

  1. Turn the ignition to the OFF position.
  2. Apply the park brake.
  3. Apply a bright incandescent light to the DRL ambient light sensor.
  4. Turn the ignition to the RUN position.
    • The headlamps are OFF.
    • The exterior lamps are OFF.

Headlamps, Daytime Running Lamps (DRL) On With Park Brake Applied

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