GM Service Manual Online
For 1990-2009 cars only

Step

Action

Normal Result(s)

Abnormal Result(s)*

1

  1. Cover ambient light sensor with a dark cloth or tape.
  2. Ensure park brake is OFF.
  3. Turn ignition to ON position.

Headlamp control module applies power to the parklamps and headlamps.

Twilight Sentinel Inoperative

2

  1. Cover ambient light sensor with a dark cloth or tape.
  2. Ensure park brake is OFF.
  3. Turn ignition to ON position.
  4. Turn ignition to OFF position.

Headlamp control module applies power to the parklamps and headlamps with ignition ON and turns parklamps OFF and continues to power headlamps (for a predetermined period amount of time) when ignition is turned to OFF.

Twilight Sentinel Inoperative

3

  1. Cover ambient light sensor with a dark cloth or tape.
  2. Set the park brake.
  3. Turn ignition to ON position.
  4. Release the park brake.
  5. Set the park brake.
  6. Turn ignition to OFF position.

Parklamps and headlamps remain OFF until park brake is released, at which time they turn ON.

When park brake is set again, parklamps and headlamps remain ON until ignition is turned to OFF position, at which time parklamps turn OFF and headlamps remain ON.

Twilight Sentinel Inoperative