Interior Lighting Systems Description and Operation. Chevrolet PJJ 2001

For 1990-2009 cars

### Interior Lamps

The interior Lamps consist of the following two groups. The first group are those lamps which may not be dimmed.

• | The Courtesy/Reading Lamps

• | The Dome lamps

• | The Vanity Mirror Lamps

• | The IP and Rear Compartment Lamps

### Courtesy Lamps

The courtesy lamps, include the roof rail/reading lamps, the footwell lamps, dome and rear view mirror lamps. The dome lamp switch has three positions, DOOR, OFF and ON. When in the DOOR position, the dome lamp operation is controlled by the BCM. The ON position provides a ground for continuous operation. The OFF position turns off any dome lamp operation. The courtesy lamps, may be manually turned on by placing the IP dimmer switch in the DOME position. When the dome lamp switch is in the DOOR position, the dome lamp will illuminate when a door is opened. When a front door is opened, the dome and courtesy lamps turn on. After all the doors have been closed the courtesy lamps will remain illuminated approximately [10] seconds after the last door closes. When the driver places the dome lamp switch in the OFF position, the dome lamp will be disabled.

The fuse in the IP junction block supplies battery positive voltage to the body control module (BCM). The inadvertent power control circuit of the BCM supplies battery positive voltage to the IP junction block. The IP junction block supplies battery positive voltage to the left and right hand courtesy lamps and the dome lamp. When any door is opened, the door jam switch contacts close and the door open input to the BCM is grounded. Some of the courtesy lamps may also be used as reading lamps by placing the lamps switch in the ON or OFF position. The rear view mirror contains two map lamps, each map lamp may be manually turned on or off using it's own switch.

If the driver inadvertently leaves any interior lamp on the BCM will turn it off after timeout.

The courtesy lamps will normally turn off using the theater dimming feature. The BCM provides a pulse width modulated ground to left and right hand courtesy/reading lamps and the dome lamp for the theater dimming feature. The courtesy lamps will also turn off immediately if a door lock command is received with all the doors closed, or if the ignition switch is turned to either the ON or RUN position.

### Keyless Entry Interior Illumination

When the driver uses the door key in order to unlock the doors, the body control module (BCM) receives a door unlock signal. The BCM must have inputs that indicate that the ignition switch is OFF, the courtesy lamp switch is OFF and all the doors are closed. The BCM will then activate the interior lamps. The courtesy lamps will remain on, approximately 10 seconds after the door is closed. The BCM will then turn them off through the theater dimming feature. If the door locks are activated to the LOCK position, or if the ignition switch is turned to either the RUN or CRANK position the courtesy lamps will turn off immediately.

When the remote function actuation (RFA) module receives a door unlock command from the remote function actuator transmitter, the RFA module will ground the door unlock signal circuit to the BCM, [send a class 2 message to the body control module (BCM),] indicating that an UNLOCK command has been received. The BCM will keep the courtesy lamps on approximately 10 seconds and then turn them off through the theater dimming feature. If the door locks are activated to the LOCK position, the courtesy lamps will deactivate immediately. When the ignition switch is turned to either the ON or RUN position the courtesy lamps will deactivate in approximately one second.

### Vanity Lamps

The inadvertent power relay also provides battery positive voltage to each vanity mirror lamp. When the vanity mirror cover on the sunshade is opened, its switch closes to provide a ground circuit and the vanity lamp illuminates.

### IP Compartment Lamp

The inadvertent power relay also provides battery positive voltage to the instrument panel compartment lamp. When the IP compartment is opened, its switch closes to provide a ground circuit and the IP compartment lamp illuminates.

### Rear Compartment Lamp

The inadvertent power relay also provides battery positive voltage to the rear compartment lamp. When the rear compartment is opened, its switch closes to provide a ground circuit and the rear compartment lamp illuminates.

The second group includes lamps which may be dimmed. This group may use a combination of vacuum fluorescent (VF) illumination and of incandescent lamps.

• | Door switches and window switches

• | HVAC control head assembly

• | Radio

• | The instrument panel cluster (IPC)

### Interior Lamps Dimming

When the ignition switch is turned to the ON position, the vacuum fluorescent (VF) displays (radio and HVAC control assembly), incandescent lamps, turn on at maximum brightness. When the park lamps are on and the ambient light sensor indicates low light conditions, all incandescent back lighting turn on at the dimming level indicated by the IP dimmer switch. At the same time all vacuum fluorescent (VF) displays dim to match the indicated dimming level. The fuse in the underhood junction block supplies battery positive voltage to the headlamp switch. With the headlamp switch in the PARK position, battery positive voltage is supplied to the junction block. The junction block supplies battery positive voltage to the instrument panel dimmer switch and the dimmer module. The dimmer module supplies a proportional voltage to the fuse in the junction block in response to the instrument panel dimmer switch. All the vacuum florescent (VF) and incandescent back lighting lamps are provided a specific voltage and are then grounded. When the headlight switch is turned to the PARK or HEAD position, all incandescent back lighting turn on at the dimming level indicated by the IP dimmer switch. When the IP dimmer switch is moved from MIN to MAX, all vacuum fluorescent (VF) [liquid crystal display LCD], [light emitting diode LED] displays, as well as all incandescent back lighting respond from Minimum intensity to maximum brightness in response to the IP dimmer switch.

The interior lamps group consists of the following:

• | Door switches and window switches

• | HVAC control head assembly

• | Radio

• | The instrument panel cluster (IPC)

• | Transaxle Shift Indicator Lamp

Driver controls include the following components.

• | The emergency flasher switch

• | The fog lamp switch

• | The headlamp dimmer switch

• | The headlamp switch

• | The interior lamp switch

• | The IP dimmer switch

• | The stoplamp switch

• | The turn signal switch