GM Service Manual Online
For 1990-2009 cars only

Step

Action

Normal Result(s)

Abnormal Result(s)*

1

  1. Move the gear selector to the PARK position.
  2. Turn the ignition switch to the ON position.
  3. Cover the ambient light sensor (windshield side) using a dark cloth.
  4. Shine a light on the headlamp sensor (mirror side).

The mirror gradually darkens.

Automatic Day-Night Mirrors Inoperative

2

Move the gear selector to the REVERSE position.

The mirror gradually lightens to a clear state.

Mirrors - Automatic Day-Night Inoperative in Reverse

3

Move the gear selector to the PARK position.

The mirror gradually darkens.

Automatic Day-Night Mirrors Inoperative

4

Remove the cloth and the light.

The mirror gradually lightens to a clear state.

Automatic Day-Night Mirrors Inoperative

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