2004 Tahoe
INTERIOR LIGHTING SYSTEMS DESCRIPTION AND OPERATION
INTERIOR LAMPS
The interior lighting consist of the following 2 groups. This first group includes lamps that may not be dimmed.
Courtesy/illuminated entry lamps
Dome lamps
Map lamps
Reading lamps
Vanity mirror lamps
COURTESY/ILLUMINATED ENTRY LAMPS
The courtesy/illuminated entry lamps, may be manually turned on or off by placing the interior lamp switch in the ON or OFF position. If an outside door handle is lifted or a door is opened, the courtesy/illuminated entry lamps illuminate. After all the doors have been closed the courtesy/illuminated entry lamps will remain illuminated approximately 15 seconds . The courtesy/illuminated entry lamps will also turn on prior to any door being opened, and remain illuminated approximately 40 seconds when the driver removes the ignition key. When the driver places the dome lamp defeat switch in the OFF position, the courtesy/illuminated entry lamps will be disabled.
The left and right front door courtesy lamps are controlled, and receive voltage and ground from the drivers door module (DDM) and the passenger door module (PDM) respectively. The body control module (BCM), DDM, and the PDM communicate through class 2 serial data for the lamp illumination commands and the door ajar switches.
The remaining courtesy lamps are controlled and receive voltage from the BCM. Voltage for the courtesy lamp supply voltage circuit and the backup lamp supply voltage circuit is from the TBC B fuse in the instrument panel fuse block directly through the BCM to these circuits. A short to ground on either of these circuits will open the fuse. Ground is provided to the footwell lamps and all courtesy/reading lamps at G203. Ground is provided to the right middle and right rear door at G306. Ground is provided to the left middle and left rear door at G302.
KEYLESS ENTRY INTERIOR ILLUMINATION
When the driver uses the door key in order to unlock the doors, the 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 15 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 driver uses the remote function actuator transmitter to unlock the doors, trunk or presses the panic button, the BCM will keep the courtesy lamps on approximately 40 seconds . When the driver uses the remote function actuator transmitter to lock the doors, the BCM will keep the courtesy lamps on approximately 2 seconds . 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 approximately 40 seconds , after an alarm event is completed.
VANITY LAMPS
The inadvertent power supply voltage circuit of the BCM provides battery positive voltage to each vanity mirror lamp. When the vanity mirror cover on the sunshade is opened, a switch closes to provide a ground circuit and the vanity lamp illuminates. In the event that any of these lamps were to remain illuminated for a period of more than 10 minutes with the ignition switch in the OFF position, the BCM will deactivate the inadvertent power supply voltage circuit to prevent a total battery discharge condition. Ground is provided to the vanity lamps at G203.
READING LAMPS
The inadvertent power supply voltage circuit of the BCM provides battery positive voltage to the reading lamps. The reading lamps and switch are integral to the courtesy/reading lamp assembly. When the switch is closed, voltage is supplied and the lamp illuminates. In the event that any of these lamps were to remain illuminated for a period of more than 10 minutes with the ignition switch in the OFF position, the BCM will deactivate the inadvertent power supply voltage circuit to prevent a total battery discharge condition. Ground is provided to the reading lamps at G203.
BATTERY RUNDOWN PROTECTION/INADVERTENT POWER
The BCM inadvertent power supply voltage circuit provides battery positive voltage to all of the interior reading lamps, visor vanity mirror lamps, and cargo lamps if equipped. In the event that any of these lamps were to remain illuminated for a period of more than 10 minutes with the ignition switch in the OFF position, the BCM will deactivate the inadvertent power supply voltage circuit to prevent a total battery discharge condition.
The BCM also utilizes the inadvertent power supply voltage circuit as a lamp request when none of the lamps in the circuit are illuminated. When a lamp switch is activated, the BCM receives the request for lamp illumination and switches to supplying voltage to the inadvertent power supply voltage circuit.
INTERIOR LAMPS DIMMING
The second group includes lamps which may be dimmed. This group may use a combination of vacuum fluorescent (VF) illumination and incandescent lamps.
When the ignition switch is turned to the RUN position, the radio VF display turns ON at maximum brightness. When the park lamps are ON, all incandescent back lighting turn on at the dimming level indicated by the instrument panel (I/P) dimmer switch. 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 incandescent back lighting lamps are provided with a specific voltage. When the I/P dimmer switch is moved from MIN to MAX, all VF displays, as well as all incandescent back lighting respond from minimum intensity to maximum brightness in response to the I/P dimmer switch.
The following switches and components have back lighting when the park lamps are on:
The instrument panel cluster (IPC)
Radio and remote CD player
Window and heated seat switches
Garage door opener switch
Sunroof switch
HVAC control assembly
Headlamp and panel dimmer switch
Multifunction accessory switch
Fog lamp switches
Rear wheel steering mode switches
Rear parking assist (RPA) disable switches
Transfer case shift control switch
Analog clock
Roof beacon switch
PRNDL lamps
Traction control switch
Steering wheel control switches
Headlamp leveling switch
The left and right front door switch illumination is controlled, receives voltage and ground from the DDM and the PDM respectively. The radio is also a class 2 module and has full control of its illumination. The BCM, DDM, PDM, and radio communicate through class 2 serial data for the lamp illumination commands
The I/P cluster illumination lamps receive voltage and are controlled by the BCM on the instrument panel lamps dimming supply voltage circuit. Ground for the instrument panel lamps is at G203.
The various switches, HVAC control assembly, and the PRNDL lamps receive voltage and are controlled by the BCM on the instrument panel lamps dimming control circuit. Ground for the rear window switches is at G302 and G306. Ground for the traction control switch, steering wheel controls, and the rear window/wiper switch is at G108. Ground for the remaining switches is at G203.
The following indicators receive voltage from the BCM and are controlled by ground or from various modules:
2 and 4 wheel steering indicators
Tow indicator
Transfer case control switch 4WD position indicators
Fog lamp indicators
Rear parking assist (RPA) disable indicator
The indicators receive voltage from the BCM on the LED dimming circuit. Ground/control for the indicators is from the various modules. Voltage for the LED dimming supply circuit, instrument panel lamps dimming control circuit and the instrument panel lamps dimming supply circuit is from the TBC A fuse in the instrument panel fuse block directly through the BCM to these circuits. A short to ground on only the instrument panel lamps dimming control circuit will open the fuse.
The modules controlling the above indicators are as follows:
Rear wheel steering control module
Transfer case shift control module
BCM
