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For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 1999 🢒 Grand Prix 🢒 Body and Accessories 🢒 Retained Accessory Power 🢒 Interior Lights Circuit Description

Courtesy Lights

Body Control Module (BCM)

The body control module (BCM) controls the interior illumination. One of 3 BCM types is installed on this vehicle based on the vehicle equipment. The BCM type 2 provides the following features:

    • The interior Illumination control
    • The inadvertent load (battery rundown) protection
    • The chime functions
    • The retained accessory power (RAP)
    • The automatic power door locks

The BCM type 3 provides the BCM type 2 features plus the keyless entry system (RPO AUO).

The BCM type 4 provides the BCM type 2 and 3 features plus the content theft deterrent (RPO UA6) with remote activation verification and remote alarm.

Interior Illumination Control

The BCM turns on the courtesy lights when the following actions occur:

    • Any of the vehicle doors are opened.
    • The IP dimmer switch is in the DOME position.
    • When the exit illumination feature is active
    • When unlocking the doors using the keyless entry transmitter (BCM types 3 and 4 only).
    • When unlocking a door using a door cylinder lock (BCM type 4 only).

The BCM turns OFF the courtesy lights when all of the doors are closed and the IP dimmer switch is OFF.

All the vehicle doors contain a door lock ajar switch. When the drivers door is open, the left front door lock ajar switch closes and sends a ground signal to the BCM through circuit 159.

When 1 of the right front, left rear or right rear doors is open, the corresponding door lock ajar switch closes and sends a ground signal to the BCM through circuit 49. The BCM grounds circuit 690 when detecting a ground signal in either circuit 49 or circuit 159.

When the drivers door is closed, the left right door lock ajar switch opens circuit 159. When the right front, left rear and right rear doors are closed, the corresponding door lock ajar switches open circuit 49. The BCM then opens circuit 690 when both circuit 49 and circuit 159 are open.

The BCM uses the voltage in circuit 240 to power the courtesy lights through circuit 1393. The BCM controls the power supplied in circuit 1393 for inadvertent load (battery rundown) protection. The BCM opens circuit 690 when the inadvertent load (battery rundown) protection is active (circuit 1393 is open).

Delayed Illumination

The BCM grounds circuit 690 for 22-28 seconds turning on the courtesy lights when the following conditions are met:

    • The delay illumination is enabled (interior lighting mode 2 or 4). Refer to Interior Lighting Modes in this section.
    • The ignition switch is in the OFF position.
    • The IP dimmer is OFF.
    • When closing all of the vehicle doors. The BCM will detect a transition from a ground signal to an open circuit in either circuit 49 or circuit 159.

The delayed illumination feature is canceled when turning the ignition switch to the ACC or RUN position or by unlocking the doors when using either a power door lock switch or a keyless entry transmitter.

Exit Illumination

The BCM grounds circuit 690 for 22--28 seconds turning on the courtesy lights when the following conditions are met:

    • The exit illumination is enabled (interior lighting mode--3 or 4). Refer to Interior Lighting Modes further information.
    • The ignition key is removed from the ignition key cylinder. The BCM detects a transition from ground to an open in circuit 80.
    • The IP dimmer switch is OFF.
    • All of the vehicle doors are closed at the time the ignition key is removed from the ignition key cylinder. Circuits 49 and 159 are open.

The exit illumination is canceled when the following conditions are met:

    • Turning the ignition switch to the ACC or RUN position.
    • Locking the doors when using either a power door lock switch or a keyless entry transmitter.
    • Re-inserting the key into the ignition cylinder within 5 seconds when the exit illumination starts.

Theater Dimming

The BCM dims the courtesy lights slowly from full brightness to off in 3 seconds. This feature starts anytime the BCM is turning off the courtesy lights. The theater dimming does not work when turning the IP dimmer switch from the DOME position to the OFF position or when the illumination feature is canceled by locking the doors with a power door lock switch. Also, the theatre dimming does not work when the exit lighting feature is canceled.

Door Key Unlock Illumination (BCM Type 4 Only)

The BCM grounds circuit 690 for 36-44 seconds turning on the courtesy lights when the following conditions are met:

    • The ignition switch is in the OFF position.
    • Either door key cylinder lock is turned to unlock a door (grounding circuit 781).

Keyless Entry Unlock Illumination (BCM Type 3 and 4 only)

The BCM grounds circuit 690 for 36-44 seconds turning on the courtesy lights when the following conditions are met:

    • The ignition switch is in the OFF position.
    • All of the vehicle doors are closed.
    • The IP dimmer switch is OFF.
    • The BCM receives a message from the remote control door lock receiver (RCDLR) in order to unlock the doors.

Inadvertent Load (Battery Rundown) Protection

The body control module (BCM) has a feature called the inadvertent load (battery rundown) protection. The BCM de-energizes circuit 1393 for 10 minutes (+/- 1 minute) after the ignition switch has been turned from the ACC or RUN position to the OFF position.

The BCM stores power to circuit 1393 when the following conditions are met:

    • Turning the ignition switch from the OFF or UNLOCK position to the ACC or RUN position
    • Removing the key from the ignition key lock cylinder
    • Opening any of the vehicle doors
    • Turning the IP dimmer switch to the DOME position
    • Turning on any of the reading lights connected to circuit 1393
    • The BCM receives a message receives a message from the RCDLR (BCM type 3 or 4 only).
    • Locking a door using a key (BCM type 4 only)

The inadvertent battery power rundown protection feature is mileage-sensitive. The vehicles with less then 15 total miles driven have a 3 minute (+/- 18 seconds) time-out instead of 10 minutes.

Feature Customization

Interior Lighting Modes

The vehicle contains the following interior lighting modes:

Delayed Illumination

    • Enabled (Interior lighting modes 2 and 4)
        The courtesy lights turn ON for 25  seconds then fade to OFF after the last door is closed.
    • Disabled (Interior lighting modes 1 and 3)
        The courtesy lights turn OFF after the last door is closed.

Exit Lighting

    • Disabled (Interior lighting modes 1 and 2)
        The courtesy lights stay off upon removing the key from the ignition switch.
    • Enabled (Interior lighting modes 3 and 4)
        The courtesy lights turn ON for 25 seconds upon removing the key from the ignition switch.

Changing the Interior Lighting Mode

Perform the following procedure in order to change the interior lighting mode:

  1. Turn the IP dimmer switch OFF.
  2. Turn the ignition switch to the OFF position.
  3. Remove the MALL PGM fuse.
  4. Turn the ignition switch to the ACC position.

    5. The BCM will sound a chime a number of times equivalent to the BCM type installed on the vehicle.

    The BCM has entered the feature customization mode.

  5. In order to advance to the interior lighting mode, cycle the IP dimmer switch from OFF to DOME then back to OFF.

    6. The BCM will sound a chime a number of times equivalent to the lighting mode. A transition past mode 4 repeats the sequence starting with mode 1.

The following lighting modes exist:

    • Mode 1- The exit illumination and delayed illumination are disabled.
    • Mode 2- The delay illumination is enabled.
    • Mode 3- The exit illumination is enabled.
    • Mode 4-The exit illumination and delayed illumination are enabled.

In order to exit and save the current customization mode, perform the following steps:

  1. Turn the ignition switch to the OFF position.
  2. Re-install the MALL PGM fuse.

Windshield Header Courtesy/Reading Lamps and Roof Rail Courtesy/Reading Lamps

The lamps have switches that allow the operator to turn the lamps ON when the courtesy lights are OFF. The switches, when turned ON, provide ground to the lamps, turning the lamps ON. The switches obtain ground through circuit 350. Power to the lamps is provided by the BCM through circuit 1393 in order to be protected by the inadvertent load (battery rundown) protection in case the lamps are left ON.

Roof Rail Courtesy Lamps, IP Courtesy Lamps and Door Courtesy Warning Lamps

The operation of the lamps is described as part of the courtesy lights operation. The BCM provides power to circuit 1393 and ground, circuit 690 to the lamps controlling their operation.

IP Dimmer Switch

The IP dimmer switch allows the operator to turn ON the courtesy lights from the inside of the vehicle. When the IP dimmer switch is in the DOME position the switch sends a ground signal to the BCM through circuit 156. This will cause the BCM to turn on the courtesy lights. When the IP dimmer switch is OFF, the BCM turns the courtesy lights OFF. The IP dimmer switch is protected by the inadvertent load (battery rundown) protection in case the ignition switch is left in the DOME position with the ignition switch OFF.

The IP dimmer switch is also used in order to change the interior lighting modes during the feature customization. Refer to Body Control System Circuit Description in Body Control System. The IP dimmer switch is also used in order to enter the Input/Output test during the BCM diagnostics.

Sunshade Illuminated Mirrors

The sunshade illuminated mirror lamps turn ON when the mirror cover is open. The sunshade illuminated mirror has a switch that closes (providing ground to the lamps) when the mirror cover is open. The switch opens when the cover is closed. the switch receives ground through circuit 350.

Power to the sunshade illuminated mirror lamps is provided by the BCM through circuit 1393 in order to be protected by the inadvertent load (battery rundown) protection in case the mirror cover is left open.

IP Compartment Lamp

The IP compartment lamp turns ON when the IP compartment is open. The IP compartment lamp has a switch that closes in order to provide voltage to the lamp when the IP compartment is open and the switch opens when the IP compartment is closed. The switch receives voltage through circuit 1393.

The IP compartment lamp receives voltage ground through circuit 1450 and voltage from the switch through circuit 148. The IP compartment lamp is protected by the inadvertent load (battery rundown) protection in case the IP compartment is left open.

Rear Compartment Courtesy Lamp

The rear compartment courtesy lamp turns on when the rear compartment lid is open. The rear compartment courtesy lamp has a switch that closes (providing ground to the lamp) when the rear compartment lid is open, and the switch opens when the rear compartment lid is closed. The rear compartment courtesy lamp receives voltage through circuits 1393 and 737 and ground through circuit 744. The inadvertent load (battery rundown) protection protects the rear compartment courtesy lamp in case the rear compartment lid is left open.

The body control module (BCM) Input/Output test consists of a series of circuit tests, turning the courtesy lights ON and OFF among other BCM outputs.

Follow the BCM Input/Output test activation procedure when indicated during the diagnosis of the interior lights.

The body control module (BCM) Input/Output test consists of a series of circuit tests, turning the courtesy lights ON and OFF among other BCM outputs.

Follow the BCM Input/Output test activation procedure when indicated during the diagnosis of the interior lights.

BCM Input/Output Test Activation
  1. Turn the IP dimmer switch OFF.
  2. Turn the ignition switch to the OFF position.
  3. Remove the MALL PGM fuse.
  4. Turn the ignition switch to the ACC position.

    5. The BCM will sound the chime a number of times equivalent to the BCM type installed on the vehicle. Refer to Body Control System Circuit Description in Body Control System.

  5. Within 1 second, turn the ignition switch from the ACC position to the OFF position then back to the ACC position.

    6. The BCM will sound any DTCs stored. Refer to Body Control Module Diagnostic Information in Body Control System.

  6. Turn the IP dimmer switch to the DOME position.

The BCM entered the Input/Output test. The BCM Input/Output consists of the following tests:

    • Test 1-- De-energizes circuit 1393. Turns OFF all of the interior lights.
    • Test 2--Energizes circuit 1393. Provides power to all of the interior lights.
    • Test 3-- Grounds circuit 690. Turns ON all the courtesy lights.
    • Test 4-- Energizes the theft deterrent relay for 1 second by grounding circuit 352. Turns ON the headlights (BCM type 4 only).
    • Test 5-- Energizes the horn relay for 25 ms by grounding circuit 28. Sounds the horn (BCM type 4 only).
    • Test 6-- Turns the theft deterrent indicator lamp ON by grounding circuit 749 (BCM type 4 only).
    • Test 7-- Turns the theft deterrent indicator lamp OFF by opening circuit 749 (BCM type 4 only).

The BCM runs the Input/Output test in numerical order.

In order to move to the next test, cycle the IP dimmer switch from the DOME position to the OFF position then back to the DOME position. The BCM will sound a chime a number of times equivalent to the Input/Output test number listed above. The Input/Output test sequence repeats until the ignition switch is turned to the OFF position.

When the BCM is performing the Input/Output test, the chime will sound when any of the BCM inputs are activated. For example, the chime will sound when opening any of the vehicle doors.