For 1990-2009 cars
Body Control Module Components
Body Control System Schematics
Ground Distribution Schematics
Interior Lights Schematics
Power Distribution Schematics

### 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 instrument panel 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 instrument panel 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 CKT 159.

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 CKT 54. The BCM grounds CKT 690 when detecting a ground signal in any of the following circuits:

• | CKT 49

• | CKT 54

• | CKT 159

When the driver door is closed, the left front door lock ajar switch opens CKT 159. When all of the right front, left rear, and right rear doors are closed, their corresponding door lock ajar switches open CKT 49. The BCM then opens CKT 690 when any one of CKTs 49, 54, or 159 is open.

The BCM uses the voltage in CKT 240 to power the interior lights through CKT 328 and CKT 1393. The BCM controls the power supplied to CKT 328 and CKT 1393 for inadvertent load (battery rundown) protection. The BCM opens CKT 690 when the inadvertent battery power rundown protection is active (CKT 1393 is open).

#### Delayed Illumination

The BCM grounds CKT 690 for 22-28 seconds, turning on the interior courtesy lamps when the following conditions exist:

1. The delay illumination customization is selected (interior lighting mode 2 or 4). Refer to Diagnostic Aids.
2. The ignition switch is in either the LOCK position or the OFF position.
3. The instrument panel dimmer switch is off.
4. The interior lamps override switch is on and the interior courtesy lights are enabled.
5. When closing all of the vehicle doors the BCM detects a transition from a ground signal to open in one of the following circuits:

• | CKT 49

• | CKT 54

• | CKT 159

The delayed illumination feature is canceled when the following conditions exist:

• | Turn the ignition to the ACC position or the RUN position

• | Use a power door lock switch in order to lock the door.

• | Use a door lock key cylinder (BCM type 4 only) in order to lock the left front and the right front or liftgate doors.

• | Use a keyless entry transmitter (BCM type 3 and type 4 only) in order to lock the doors.

#### Exit Illumination

The BCM grounds CKT 690 for 22-28 seconds, turning on the interior (courtesy) lamps when the following conditions are met:

• | The exit illumination customization is selected (interior lighting mode 3 or 4). Refer to Diagnostic Aids.

• | The ignition key is removed from the ignition key cylinder and the BCM detects a transition from ground to open in CKT 80.

• | The IP dimmer switch is in the OFF position (CKT 156 is open).

• | All the vehicle doors are closed at the time the ignition key is removed from the ignition key cylinder (CKTs 49 and 159 are open).

The exit illumination is canceled when one of these conditions is met:

• | Turn the ignition switch to the ACC or RUN position.

• | Lock the doors when using either a power door lock switch or a keyless entry transmitter.

• | Re-insert the key into the ignition cylinder within 5 seconds after exit illumination starts.

#### Theatre Dimming

The BCM dims the interior courtesy lights slowly from full brightness to off in 3 seconds. This feature starts anytime the BCM turns off the interior courtesy lights. Theatre dimming does not operate when the following conditions exist:

• | The IP dimmer switch is turned from the DOME position to the OFF position.

• | The illumination feature is cancelled by locking the doors with the power door lock switch.

• | The exit lighting feature is cancelled.

#### Interior Illumination DIM to OFF

The BCM dims the interior courtesy lamps slowly from full intensity to off in 3 seconds. This feature starts anytime the BCM opens CKT 690. This dimming feature does not work when you turn the instrument panel 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, this dimming feature does not work when the exit lighting feature is canceled.

#### Door Key Unlock Illumination (BCM Type 4 Only)

A BCM type 4 grounds CKT 690 for 36-44 seconds. The interior courtesy lamps turn on when the following conditions exist:

• | The ignition switch is in either the LOCK position or the OFF position.

• | The interior lamp override switch is on and the interior courtesy lights are enabled.

• | One of the following doors is unlocked using a door key cylinder lock. This action grounds CKT 781:

- | The left front door

- | The right front door

- | The liftgate door

#### Keyless Entry Unlock Illumination (BCM Type 3 and 4 Only)

A BCM type 4 grounds CKT 690 for 36-44 seconds, turning on the interior (courtesy) lamps when the following conditions are met:

• | The ignition switch is in either the LOCK position or the OFF position.

• | All the vehicle doors are closed.

• | The instrument panel dimmer switch is off.

• | The interior lamps override switch is on and the interior courtesy lights are enabled.

### Conditions for Setting the DTC

The BCM detects a short to B+ in CKT 690.

### Action Taken When the DTC Sets

• | The BCM sets the diagnostic trouble codes (DTC) 3.

• | The interior courtesy lamps do not illuminate.

### Conditions for Clearing the MIL/DTC

• | A short to B+ in CKT 690 is no longer present between the BCM and any of the courtesy lamps.

• | After the repairs are completed the DTC is cleared. Refer to Clearing Diagnostic Trouble Codes.

### Diagnostic Aids

• | Inspect for a short to B+ in CKT 690.

• | Perform the following while moving the wiring and the connectors. This will cause the malfunction to appear.

#### Interior Lighting Modes

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

1. Turn off the instrument panel dimmer switch.
2. Turn the ignition switch to the OFF position.
3. Remove the MALL PGM 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 customization mode. In order to change the interior lighting, cycle the IP 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.

#### BCM Input/Output Test Procedure

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

The BCM sounds the chime a number of times equal to the BCM type installed on the vehicle.

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

The BCM sounds any DTCs that are stored.

6. Turn the instrument panel 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 CKT 1393 (protected courtesy lamp output).

• | Test 2 energizes CKT 1393.

• | Test 3 grounds CKT 690 (courtesy lamps control).

• | Test 4 energizes the theft deterrent relay for 1 second by grounding CKT 352. Turns on the headlamps (BCM type 4 only).

• | Test 5 energizes the horn relay for 25 ms by grounding CKT 28. Sounds the horn (BCM type 4 only).

• | Test 6 turns on the theft deterrent indicator lamp by grounding CKT 749 (BCM type 4 only).

• | Test 7 turns off the theft deterrent indicator lamp by opening CKT 749 (BCM type 4 only).

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

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

### Test Description

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

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

2. Test the BCM to see if the BCM is able to control the courtesy lights CKT 690.

3. Test for a short to B+ in CKT 690.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the BCM diagnostic system check? | -- | Go to Step 2 | Go to Diagnostic System Check - Body Control System
2 | Perform the BCM Input/Output test. Refer to Diagnostic Aids. Do all the lights connected to CKT 690 turn on when the BCM Input/Output performs test 3? | -- | Go to Step 4 | Go to Step 3
3 |

1. Turn the ignition switch to the LOCK position.
2. Disconnect the BCM connector C1.
3. Turn the ignition switch to the RUN position.
4. Use the J 39200 digital multimeter (DMM) in order to measure the voltage between the BCM harness connector C1 terminal F and ground.

Is the voltage less than the specified value?

2V

Go to Step 5

Go to Step 6

4 | The malfunction is not present at this time. Refer to Diagnostic Aids. Is the action complete? | -- | Go to Step 7 | --
5 |

1. Inspect the BCM connector C1 terminal F for a short to B+. Repair the short as needed.
2. If the connector is not faulty, replace the BCM. Refer to Body Control Module Replacement

Is the repair complete?

--

Go to Step 7

--

6 | Repair short to B+in CKT 690. Refer to Interior Lights. Is the repair complete? | -- | Go to Step 7 | --
7 |

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 System Check - Body Control System

System OK