GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2001 🢒 Montana 🢒 DTC 🢒 DTC 003

Circuit Description

The Body Control Module (BCM) controls the interior illumination. The BCM turns on the interior courtesy lamps when the following actions occur:

    • Any of the vehicle doors are opened.
    • The dimmer switch is turned to the DOME position.
    • Exit illumination is active.
    • The doors are unlocked through the keyless entry system (BCM type 3 and type 4 only).
    • The doors are unlocked using the door key cylinder (BCM type 4 only).

The BCM turns the interior lamps off when all the vehicle doors are closed and the dimmer switch is in the OFF position.

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

When one of the right front, left rear, or right rear doors is open, its corresponding door lock ajar switch closes and sends a ground signal to the BCM through the corresponding door ajar input circuit. The BCM grounds the courtesy lamps low control circuit when detecting a ground signal in any of the following circuits:

    • Driver door switch signal circuit
    • Sliding door switch signal circuit
    • Door open switch signal circuit

When the driver door is closed, the left front door lock ajar switch opens the driver door switch signal circuit. When any door is closed, their corresponding door lock ajar switch opens the corresponding door switch signal circuit. The BCM opens the courtesy lamps low control circuit when all of the door switch signal circuits are open.

The BCM powers the interior lights through the courtesy lamps supply voltage circuit. The BCM deactivates the courtesy lamps supply voltage circuit during inadvertent load battery rundown protection. The BCM also opens the courtesy lamps low control circuit when the inadvertent battery power rundown protection is active.

Conditions for Setting the DTC

The BCM detects a short to ground or battery voltage in courtesy lamps low control circuit.

Action Taken When the DTC Sets
    • The BCM sets the diagnostic trouble code (DTC) 3.
    • The courtesy lamps are disabled when the courtesy lamps low control circuit is shorted to battery voltage.
    • The courtesy lights remain on when the courtesy lamps low control circuit is shorted to ground.

Conditions for Clearing the MIL/DTC
    • A short to battery voltage in the courtesy lamps low control circuit is no longer present between the BCM and any of the courtesy lamps.
    • A short to ground in the courtesy lamps low control circuit is no longer present between the BCM and any of the courtesy lamps.
    • After the repairs are completed, clear the DTC. Refer to On-Board Diagnostic Features .

Diagnostic Aids
    • If the problem is intermittent, the diagnostic code may still set. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    • The following conditions may cause an intermittent malfunction to occur:
       - Inspect for an intermittent short to battery voltage in the courtesy lamp low control circuit.
       - Inspect for an intermittent short to ground in the courtesy lamp low control circuit.

Interior Lighting Modes

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

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

The BCM sounds the chime a number of times equivalent to the BCM type installed on the vehicle. At this time the BCM has entered the feature customizing mode. In order to change the interior lighting, cycle the dimmer switch from the OFF position to the DOME position and then back to the OFF position. The BCM sounds a chime a number of times equal to the lighting mode.

The lighting modes are as follows:

    • Mode 1 - Exit illumination and delayed illumination are disabled.
    • Mode 2 - Delay illumination is enabled.
    • Mode 3 - Exit illumination is enabled.
    • Mode 4 - Exit illumination and delayed illumination are enabled.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Always perform the lighting diagnostic system check before attempting to diagnose DTC 3.

    2.

  2. Tests for a short to voltage in the courtesy lamps low control circuit.

    3.

  3. If all the courtesy lamps illuminate when the courtesy lamps supply voltage is connected to battery voltage, the courtesy lamps low control circuit has a short to ground.

Step

Action

Yes

No

Schematic Reference: Interior Lights Schematics

1

Did you perform the lighting diagnostic system check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2
  1. Close all the doors.
  2. Place the IP dimmer switch in the OFF.
  3. Turn the Interior Lamps Override Switch ON in order to enable the interior lamps.
  4. Turn the ignition switch to RUN.

Are the footwell courtesy lamps illuminated?

Go to Step 4

Go to Step 3

3

  1. Disconnect the BCM connector C1.
  2. Probe the courtesy lamps low control circuit of the BCM connector C1 with a test lamp that is connected to a good ground.
  3. Turn the ignition to RUN.

Does the test lamp illuminate?

Go to Step 5

Go to Diagnostic Aids

4

  1. Disconnect the BCM connector C1.
  2. Connect a 10 amp fused jumper between the courtesy lamps supply voltage circuit and battery voltage.

Do the footwell courtesy lamps illuminate?

Go to Step 6

Go to Step 7

5

Repair a short to voltage in the courtesy lamps low control circuit of the BCM. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

Go to Step 8

--

6

Repair a short to ground in the courtesy lamps low control circuit of the BCM. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

Go to Step 8

--

7

Replace the BCM. Refer to Body Control Module Replacement in Body Control System.

Is the repair complete?

Go to Step 8

--

8
  1. Turn the ignition switch to the LOCK position.
  2. Reinstall the connectors/components removed.
  3. Remove the BCM PRGRM Fuse.
  4. Turn the ignition switch to the ACC position. The BCM sounds the chime a number of times equivalent to the BCM type installed on the vehicle.
  5. Within 1 second, turn the ignition switch from the ACC position, to the LOCK position, then back to the ACC position. The BCM sounds any DTCs stored.

Are any BCM DTCs present?

Go to Diagnostic Trouble Code (DTC) List in Body Control System

System OK