GM Service Manual Online
For 1990-2009 cars only

The twilight sentinel (TS) is a BCM feature that will turn on the low beam headlamps and the park lamps and adjust the interior lighting. This is accomplished when the ignition switch is in the ON position and the headlamp automatic control ambient light sensor indicates darkness.

There is a fixed delay of 2 seconds transition from day to night illumination, and a fixed delay of 40 seconds transition from night to day illumination. In addition, there is an added variable delay which can be adjusted from 10 seconds to 180 seconds (  minutes).

The twilight sentinel indicator is also controlled by the BCM. B+ is supplied to the twilight sentinel indicator by fuse #15. When the twilight sentinel switch is turned to the OFF position, the BCM internally grounds terminal C14 of the BCM connector C2. This provides a ground to turn the twilight sentinel indicator on.

The headlamps required indicator in the instrument cluster will be turned on by the BCM if the ignition is on and the following conditions are met:

    • The low beams are not active.
    • The shift lever is not in the PARK position.
    • The headlamp automatic control ambient light sensor indicates darkness.