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.
    • The low beam headlamps are on.
    • The high beam headlamps are off.

Headlamps Inoperative - Low Beams

2

Turn the headlamp switch to the HIGH position.

    • The high beam headlamps are on.
    • The high beam indicator is on.
    • The low beam headlamps are off.

Headlamps Inoperative - High Beams

3

  1. Turn the headlamp switch OFF.
  2. Turn the ignition ON.
  3. Apply a bright light to the daytime running lamps (DRL) ambient light sensor.

The high 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:

    • The high beam headlamps turn off.
    • The low beam headlamps turn on.
    • The exterior lamps turn on.
    •  Park Lamps Inoperative

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 ON position.
    • The headlamps are off.
    • The exterior lamps are off.
    • Headlamps - Low Beams On with Headlamp Switch Off

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