GM Service Manual Online
For 1990-2009 cars only

Body Control Module

The body control module  (BCM) controls the interior lights based on inputs it receives from the following switches:

    • The right and left side door lock switches
    • The IP dimmer switch
    • The rear compartment lid ajar indication switch

Dome Lamp, Courtesy Lamps and Reading Lamps

Voltage is applied through circuit  149 from the BCM to the following lamps on coupes:

    • The dome lamp
    • The inside rearview mirror courtesy/reading lamps

Voltage is applied through circuit  149 from the BCM to the following lamps on convertibles:

    • The right and left rear courtesy lamps
    • The rear compartment lamp
    •  The inside rearview mirror courtesy/reading lamps

The BCM provides a ground through circuit 156 and the lamps illuminate when the following actions occur:

    • The driver door is opened
    • The rear compartment is opened
    • The IP dimmer switch is moved to the on position
    • The vehicle is unlocked using the keyless entry function

The inside rearview mirror contains switches which provide ground through circuit  750 to allow manual operation of the reading lamps.

IP Compartment Lamp

Ground is applied from G200 through circuit  650 to the IP compartment lamp. When the IP compartment door is opened, voltage is applied by the BCM through circuit  149 to the IP compartment lamp.

Delayed Illumination

The BCM keeps the interior lights on for approximately 25 second after the doors and rear compartment are closed. The BCM gradually decreases the voltage on circuit 149 until the lamps are off. The lamps immediately go out under either of the following conditions:

    • The ignition switch is turned to the run or start position.
    • The vehicle doors are locked.

Exit Lighting

The BCM illuminates the courtesy lamps for approximately thirty seconds after the ignition key is removed from the ignition switch. The lamps immediately go out under either of the following conditions:

    • The ignition key is reinserted into the ignition switch.
    • The vehicle doors are locked.

Illuminated Entry

When the remote control door lock transmitter is used to access the vehicle, the BCM applies voltage through circuit  149 to the interior lights. The lights remain illuminated for approximately 40 seconds or until the ignition is turned to the start position.

Inadvertent Power Control

The BCM turns off lamps that are left on to conserve battery power. The BCM removes voltage from circuit  149 and all lamps are turned off 10 minutes after the ignition switch is turned to the off position. After the 10 minute period, the BCM turns the lamps back on under any of the following conditions:

    • Either door is opened.
    • The rear compartment is opened.
    • The IP compartment is opened.
    • Either of the courtesy/reading lamp switches are turned on.
    • The remote control door lock transmitter is used to perform any function.