GM Service Manual Online
For 1990-2009 cars only

The interior lamps system consists of 2 main features. Illuminated entry and a battery saver feature that will turn the interior lights off after 20 minutes if they are left On with all doors closed and the ignition Off. The body control module (BCM) controls both of these functions. Battery power is supplied by the BCM through CKT 1732 to the following lamps:

    • The dome lamp
    • The map lamps
    • The rear reading lamps
    • The rear dome lamp
    • The cargo lamp
    • The glove compartment lamp
    • The courtesy lamps
    • The sunshade lamps

The BCM also controls the ground circuit side of the dome lamp and reading lamps for illuminated entry. The dome lamp and reading lamp will remain on for 20 seconds after the ignition key is removed and the last door is closed. In addition, if the vehicle is equipped with remote keyless entry (RKE), the dome and reading lamps will turn On and stay on for 20 seconds after an UNLOCK signal is received from the keyless entry transmitter.

The reading lamps, dome lamp and map lamps can be turned On at any time by moving the appropriate switch to the On position.

The rear dome lamp is fed battery voltage through CKT 1732 from the BCM, through the liftgate ajar switch, and is grounded through CKT 650 to the rear ground splice pack. The rear dome lamp will turn on when the liftgate is opened. The cargo lamp is fed battery voltage through CKT 1732 from the BCM, through CKT 744 and grounded through the decklid ajar switch.

The courtesy lamps are fed battery power through CKT 1732 and are grounded through CKT 745-- left front, CKT 747--left rear, CKT 748--right rear, CKT 746--right front. These circuits will ground through the door jamb switches. The courtesy lamp will be illuminated when the affected door is opened. For example, when the right rear door is opened, the right rear door courtesy lamp will turn on.

Interior Lamps Dimming

The dimming of the interior lamps is done through the dimmer switch, located on the left lower corner of the instrument panel (I/P). The dimmer switch is fed 5 volts from the BCM through CKT 1359. The voltage flows through the variable resistor of the dimmer switch and back to the BCM through CKT 1381. The BCM receives this signal and controls the intensity of the interior lamps. The following lamps are affected:

    • The traction/heated seat switch
    • The fog lamp/heated seat switch
    • The hazard switch
    • The HVAC control head
    • The I/P cluster
    • The radio
    • The electronic Park, Reverse, Neutral, Drive, Low (PRNDL) module
    • The cigar lighter

The headlamp switch must be in the PARK or Headlamp position in order for the interior lamps dimming feature to operate.