Operation

OPERATION

Following are paragraphs that briefly describe the operation of each of the major exterior lighting systems. The lamps and the hard wired circuits between components related to the exterior lighting system may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds.

However, conventional diagnostic methods will not prove conclusive in the diagnosis of the exterior lighting system or the electronic controls or communication between modules and other devices that provide some features of the exterior lighting system. The most reliable, efficient, and accurate means to diagnose the exterior lighting system or the electronic controls and communication related to exterior lighting system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.

BACKUP LAMPS

The backup (or reverse) lamps have a path to ground at all times through a takeout and eyelet terminal of the headlamp and dash wire harness that is secured by a ground screw to the inner fender support within the engine compartment. On vehicles with a manual transmission, the backup lamp switch provides an input to the Totally Integrated Power Module (TIPM) and the TIPM provides battery voltage to the backup lamps on the backup lamp feed circuit whenever the ignition switch is in the ON position and the REVERSE position is selected with the transmission shift linkage.

On vehicles with an automatic transmission, the Powertrain Control Module (PCM) continually monitors a hard wired multiplex input from the Transmission Range Sensor (TRS), then sends the proper electronic transmission gear selector status messages to other electronic modules over the Controller Area Network (CAN) data bus. Whenever the ignition switch is in the ON position and the TIPM receives an electronic message indicating the status of the transmission gear selector is REVERSE, it provides a battery voltage output to the backup lamps on the backup lamp feed circuit.

BRAKE LAMPS

The brake (or stop) lamps each have a path to ground at all times through a takeout and eyelet terminal of the headlamp and dash wire harness that is secured by a ground screw to the left inner fender support within the engine compartment. The Center High Mounted Stop Lamp (CHMSL) has a path to ground at all times through a takeout and eyelet terminal of the instrument panel wire harness that is secured by a ground screw to the back of the support structure of the instrument panel near the center. The brake lamps and CHMSL receive battery voltage on the brake lamp switch feed circuit when the brake lamp switch is closed by the brake pedal arm. The CHMSL and brake lamps are connected to a hard wired output from the brake lamp switch. The brake lamp function of the trailer tow wiring is controlled by an output from the TIPM based upon a hard wired input from the brake lamp switch.

DAYTIME RUNNING LAMPS

Vehicles manufactured for sale in Canada illuminate the high beam filament of both headlamp bulbs at a reduced intensity when the engine is running, the parking brake is released and the exterior lamps are turned OFF. The TIPM must be programmed appropriately for this feature to be enabled. Once enabled, anytime the TIPM receives electronic messages over the CAN data bus from the PCM indicating the engine is running and from the EMIC indicating the status of the headlamp switch exterior lighting input is OFF and that the parking brake is released, the TIPM provides a pulse width modulated voltage output to the proper headlamp bulb filaments through the right and left high beam feed circuits to produce illumination at a reduced intensity.

FRONT FOG LAMPS

Vehicles equipped with optional front fog lamps include a front fog lamp switch integral to the headlamp switch on the instrument panel. The front fog lamps have a path to ground at all times through their connection to the headlamp and dash wire harness. The headlamp and dash wire harness has takeouts with eyelet terminals that are secured by ground screws to the left inner fender support within the engine compartment. The EMIC monitors a hard wired multiplex input from the headlamp switch to determine whether the fog lamps are selected, then sends electronic fog lamp switch status messages to the TIPM over the CAN data bus.

When the TIPM receives a fog lamp switch status message it then controls front fog lamp operation by providing a battery voltage output to the fog lamps through the fog lamp feed circuit. The TIPM also sends the appropriate electronic message back to the EMIC to illuminate or extinguish the front fog lamp indicator. The TIPM will automatically de-energize the front fog lamps any time the headlamp high beams are selected.

The TIPM also provides a battery saver (load shedding) feature for the front fog lamps, which will turn these lamps OFF if they are left ON for more than about eight minutes with the ignition switch in the LOCK position, if there is a charging system failure, or if the electrical system voltage falls below about 11.75 volts for more than about 30 seconds.

Each front fog lamp includes an integral adjustment screw to be used for static aiming of the fog lamp beams.

HAZARD WARNING LAMPS

The hazard warning system includes the EMIC, the TIPM and the multi-function switch on the steering column. The EMIC monitors a hard wired multiplex input from the multi-function switch to determine the status of the hazard warning switch, then sends the appropriate electronic hazard switch status messages to the TIPM over the CAN data bus. The TIPM responds to these messages by controlling a battery voltage output and the flash rate for each of the right and left turn signal lamps. The TIPM also sends the appropriate electronic messages back to the EMIC to control the illumination and flash rate of the right and left turn signal indicators, as well as to control the click rate of an electromechanical relay soldered onto the EMIC electronic circuit board that emulates the sound emitted by a conventional hazard warning flasher.

HEADLAMPS

The headlamp system includes the EMIC, the TIPM, the multi-function switch on the steering column and the headlamp switch on the instrument panel. The headlamp bulbs have a path to ground at all times through their connection to the headlamp and dash wire harness. The headlamp and dash wire harness has takeouts with eyelet terminals that are secured by ground screws to the right (right headlamp bulb) and left (left headlamp bulb) inner fender support within the engine compartment.

The EMIC monitors a hard wired multiplex input to determine the status of the headlamp switch, and a hard wired multiplex input from the multi-function switch to determine whether the high or low beams are selected. The EMIC then sends the appropriate electronic headlamp switch and headlamp beam select switch status messages to the TIPM over the CAN data bus. The TIPM responds to these messages by providing a pulse width modulated voltage output to the proper headlamp bulb through the right and left low and high beam feed circuits to illuminate the selected headlamp filaments. When the optical horn feature is selected, the low beams will shut OFF about 200 milliseconds after the high beams are activated.

The TIPM also remembers which beams (low or high) were selected when the headlamps were last turned OFF, and energizes those beams again the next time the headlamps are turned ON. The TIPM provides a battery saver (load shedding) feature for the headlamps, which will turn these lamps OFF if they are left ON for more than about eight minutes with the ignition switch in the LOCK position. The EMIC provides a fail-safe feature for the headlamps, which will send an electronic message to the TIPM to turn the low beam headlamps ON automatically if it detects no input from the headlamp switch. The TIPM also provides a fail-safe feature for the headlamps that will turn the headlamps ON automatically whenever a loss of CAN bus communication is detected with the ignition switch in the ON position.

Each headlamp includes an integral reflector adjustment screw to be used for static aiming of the headlamps.

PARK LAMPS

The park lamps system includes the EMIC, the TIPM and the headlamp switch on the instrument panel. The front park lamp and side marker lamp bulbs each have a path to ground at all times through their connection to the headlamp and dash wire harness. The headlamp and dash wire harness has takeouts with eyelet terminals that are secured by ground screws to the right (right park lamp and side marker lamp bulbs) and left (left park lamp and side marker lamp bulbs) inner fender support within the engine compartment. The rear park lamp, side marker lamp, license plate lamp and the optional fender and tailgate marker lamp bulbs have a path to ground at all times through a takeout and eyelet terminal of the headlamp and dash wire harness that is secured by a ground screw to the left inner fender support within the engine compartment. The optional cab clearance lamps each have a path to ground at all times through a takeout and eyelet terminal of the instrument panel wire harness that is secured by a ground screw to the back of the support structure of the instrument panel near the center.

The EMIC monitors a hard wired multiplex input from the headlamp switch, then sends the appropriate electronic headlamp switch status messages to the TIPM over the CAN data bus. The TIPM responds to these messages by providing a battery voltage output to the appropriate lamp bulbs through the right and left park lamps feed circuits.

The TIPM provides a battery saver (load shedding) feature for the park lamps, which will turn these lamps OFF if they are left ON for more than about eight minutes with the ignition switch in the LOCK position. The EMIC provides a fail-safe feature for the park lamps, which will send an electronic message to the TIPM to turn these lamps ON automatically if it detects no input from the headlamp switch. The TIPM also provides a fail-safe feature for the park lamps that will turn the headlamps and park lamps ON automatically whenever a loss of CAN bus communication is detected with the ignition switch in the ON position.

TRAILER TOW WIRING

In addition to the trailer tow wiring provisions, the TIPM in all vehicles includes dedicated trailer tow battery, trailer tow park lamp, and both right and left trailer tow stop/turn feed output circuits. When the TIPM receives the appropriate inputs for normal park, turn signal, hazard warning or brake lamp operation, it responds by providing battery voltage through the appropriate trailer tow wiring feed circuits to synchronize the illumination and flash rate of the trailer park, brake and turn signal lamps with those of the tow vehicle.

TURN SIGNAL LAMPS

The turn signal lamps system includes the EMIC, the TIPM and the multi-function switch on the steering column. The front turn signal lamp bulbs each have a path to ground at all times through their connection to the headlamp and dash wire harness. The headlamp and dash wire harness has takeouts with eyelet terminals that are secured by ground screws to the right (right front turn signal lamp bulb) and left (left front turn signal lamp bulb) inner fender supports within the engine compartment. The rear turn signal lamp bulbs have a path to ground at all times through a takeout and eyelet terminal of the headlamp and dash wire harness that is secured by a ground screw to the left inner fender support within the engine compartment.

The EMIC monitors a hard wired multiplex input from the multi-function switch to determine the status of the turn signal switch, then sends the appropriate electronic turn signal switch
status messages to the TIPM over the CAN data bus. The TIPM responds to these messages by controlling a battery voltage output and the flash rate for either the right or left turn signal lamps. The TIPM also sends the appropriate electronic messages back to the EMIC to control the illumination and flash rate of the right or left turn signal indicators, as well as to control the click rate of an electromechanical relay soldered onto the EMIC electronic circuit board that emulates the sound emitted by a conventional turn signal flasher.

The EMIC also provides a turn signal ON warning that will generate repetitive chimes to indicate that a turn signal has been active continuously for 1.6 kilometers (1 mile) with the vehicle speed greater than 22 kilometers-per-hour (15 miles-per-hour). Vehicles built for markets other than the United States and Canada have a revised distance threshold of 4 kilometers (2.49 miles) for this feature. The chime will continue until the turn signal input becomes inactive or until the vehicle speed message indicates that the speed is less than 22 kilometers-per-hour (15 miles-per-hour), whichever occurs first.