Description

DESCRIPTION

LAMP SYSTEMS


Lighting circuits are protected by fuses. Lighting circuits require an overload protected power and high side drivers source, ON/OFF device, lamps and body grounds to operate properly. Plastic lamps require a wire in the harness to supply body ground to the lamp socket. Replace sockets and bulbs that are corroded.


Some of the interior and exterior lighting functions are governed by the Body Control Module (BCM). The headlamp, dome, and the door ajar switches provide signals to the BCM. The BCM in turn sends a Programmable Communication Interface (PCI) bus message to the Front Control Module (FCM) to enable the necessary drivers to set the required illumination configuration.


Wire connectors can make intermittent contact or become corroded. Before coupling wire connectors, inspect the terminals inside the connector. Male terminals should not be bent or disengaged from the insulator. Female terminals should not be sprung open or disengaged from the insulator. Bent and sprung terminals can be repaired using needle nose pliers and pick tool. Corroded terminals appear chalky or green. Corroded terminals should be replaced to avoid recurrence of the problem symptoms.


Begin electrical system failure diagnosis by testing related fuses in the fuse block and intelligent power module. Verify that bulbs are in good condition and test continuity of the circuit ground. Refer to the appropriate wiring information.


AUTOMATIC HEADLAMP SYSTEM


The Automatic Headlamp system turns the instrumentation and exterior illumination lamps ON when the ambient light levels are Night and the engine RPM is 450 or above, and OFF when light levels are Day.


DAYTIME RUNNING LAMPS


Operating the high-beam headlamps at reduced power provides daytime running lamps, which are required on all new Canadian vehicles. Daytime running lamps are functional when 450 rpm's are reached.


HEADLAMPS ON WITH WINDSHIELD WIPERS


For vehicles equipped with the Automatic Headlamp System, the instrumentation and exterior illumination lamps will be turned ON when the headlamp switch is in the AUTO position, RPM > 450 and the windshield wipers have been in the intermittent, low or high mode of operation for more than ten seconds. When the windshield wipers are turned OFF the Body Control Module will determine if the instrumentation and exterior illumination lamps should remain ON base upon the current ambient light level.


HEADLAMP SYSTEM


The configuration of the headlamp system of headlamps, park lamps and fog lamps is determined by the BCM. The BCM determines the lighting configuration as a result of the inputs from the ignition switch, headlamp switch and multi-function switch. A PCI bus is transmitted from the BCM to the FCM to enable the necessary drivers to set the illumination configuration. Four wires are connected between the headlamp switch and the BCM. The first wire contains information regarding the position of the headlamp switch (Off, Automatic Headlamps, Automatic Headlamp switch fog, Park with Fog, Head, or Head with Fog Lamps). The second wire contains information regarding the position of the dimmer switch (Dome Lamp, Daytime Brightness, Dimming Level or Off). The third wire is a dedicated signal return (ground) wire. The fourth wire provides power to the front fog lamp indicator.


HEADLAMP TIME DELAY SYSTEM


The headlamp time delay system is controlled by the Body Control Module (BCM) via a PCI bus message transmitted by the BCM to the FCM to turn off the headlamps.