Interior Lighting Systems

Interior Lighting Systems Description and Operation

Interior Lamps

The interior lighting consists of the following 2 groups. This first group includes lamps that illuminate the interior and may not be dimmed.

* The cargo lamp
* The dome lamp
* The footwell lamps
* The reading lamps

Courtesy Lamps

The courtesy lamps include the reading lamps, footwell lamps, cargo lamp, and dome lamps. The cargo lamp, footwell lamps, and dome lamp may be manually turned ON by placing the I/P dimmer switch in the full up (ON) position. When the driver places the dome lamp defeat switch in the OFF position, the dome lamp, cargo lamp, and footwell courtesy lamps will be disabled. If a door is opened, the courtesy lamps, except the cargo lamp will illuminate. After all the doors have been closed, the courtesy lamps will remain illuminated approximately 15 seconds after the last door closes. The courtesy lamps will also turn ON prior to any door being opened and will remain illuminated approximately 40 seconds when the driver removes the ignition key. The body control module (BCM) will immediately turn OFF the courtesy lamps if a door lock command is received with all of the doors closed, or if the ignition switch is turned to either the ON or RUN position. Individual power and ground circuits to each lamp are supplied by the BCM.

The reading lamps can be activated individually by the switches integrated within the inside rearview mirror. Voltage is supplied by the BCM through the dome lamp circuit.

The cargo lamp is located on the rear of the vehicles cab exterior and is supplied voltage by a dedicated cargo lamp control circuit. Cargo lamp operation is controlled by placing the I/P dimmer switch in the full up (ON) position. With the I/P dimmer switch in the ON position the dome lamps, footwell lamps, and cargo lamps will illuminate. The following conditions must be met for the cargo lamp to operate:

* Parking brake APPLIED - vehicles equipped with manual transmission
* Transmission in PARK - vehicles equipped with automatic transmission

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 illuminate the interior lamps. The courtesy lamps will remain illuminated for approximately 15 seconds after the door is closed. 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 driver uses the remote function actuator transmitter to unlock the doors or presses the panic button, the BCM will keep the courtesy lamps ON for approximately 15 seconds. If the door locks are activated to the UNLOCK or LOCK position or if the ignition switch is turned to either the RUN or CRANK position, the courtesy lamps will turn OFF immediately. The BCM will also keep the courtesy lamps ON for approximately 40 seconds after an alarm event is completed.

Battery Rundown Protection/Inadvertent Power

The body control module (BCM) inadvertent power courtesy lamps supply voltage circuit provides battery positive voltage to all of the interior courtesy lamps. In the event that any of these lamps were to remain illuminated for a period of more than 20 minutes with the ignition switch in the OFF position, the BCM will deactivate the inadvertent power courtesy lamps supply voltage circuit to prevent a total battery discharge condition. Only when the ignition switch is cycled back to the RUN position will the BCM reset the internal timer and reactivate the inadvertent power courtesy lamps supply voltage circuit.

The BCM also utilizes the inadvertent power courtesy lamps supply voltage circuit as a courtesy lamp request signal circuit when none of the lamps in the circuit are illuminated. When a reading lamp switch is activated, the BCM receives the request for lamp illumination and switches to supplying voltage to the inadvertent power courtesy lamps supply voltage circuit.

Interior Switch and Control Illumination

The first group includes components that are supplied voltage through the FRT PARK LAMP fuse and the REAR PARK LAMP #2 fuse and cannot be dimmed. These lamps will be illuminated at full intensity whenever the park lamps are ON.

* Door lock and window switches
* Instrument panel (I/P) switch assembly
* Mirror switch

The second and third groups include lamps which illuminate the interior switches, controls and displays. These items can be dimmed and use a combination of LEDs, incandescent lamps, and vacuum fluorescent (VF) displays.

This second list includes components that are supplied voltage through the body control module (BCM).

* Hazard switch
* Headlamp and panel dimmer switch
* HVAC control head assembly
* Traction control switch
* Transfer case control switch

The third list of components are controlled via a serial communication signal from the BCM.

* Instrument panel cluster (IPC)
* Radio

When the ignition switch is turned to the RUN position, the radio VF displays turn ON at maximum brightness. When the park lamps are ON, all dimmable incandescent back lighting illuminate at the dimming level indicated by the I/P dimmer switch and all the other back lighting lamps illuminate at full intensity. At the same time all VF displays dim to match the indicated dimming level. The panel dimmer switch potentiometer is an input to the BCM. When the driver selects a dimming setting by moving the I/P dimming switch potentiometer, all dimmable incandescent back lighting lamps are provided with a specific voltage. The voltage depends on the position of the I/P dimmer switch and is within a range of 0.6 Volts for the MIN setting to 4.5 Volts for the MAX setting. When the I/P dimmer switch is moved from MIN to MAX, all VF displays, as well as all dimmable incandescent back lighting respond from minimum intensity to maximum brightness in response to the I/P dimmer switch.