Exterior Lighting
DIAGNOSIS AND TESTING - EXTERIOR LIGHTING
WARNING: To avoid serious or fatal injury on vehicles equipped with airbags, disable the Supplemental Restraint System (SRS) before attempting any steering wheel, steering column, airbag, seat belt tensioner, impact sensor, or instrument panel component diagnosis or service. Disconnect and isolate the battery negative (ground) cable, then wait two minutes for the system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the SRS. Failure to take the proper precautions could result in accidental airbag deployment.
WARNING: To avoid serious or fatal injury when working on the High Intensity Discharge (HID) headlamp system, be certain to take the proper precautions. The headlamp switch must be in the OFF position. Disconnect and isolate the battery negative cable. There is a risk of fatal injury caused by contact with high voltage used in the HID headlamps. There is a risk of explosion or fire caused by highly flammable materials in the vicinity of damaged HID lighting elements. There is a risk of injury caused by exposure to Ultra Violet (UV) light, a risk of burns caused by high component operating temperatures, a risk of mercury poisoning through glass splinters produced by bursting HID lighting elements. There is also a risk of poisoning caused by inhalation of mercury vapors and by toxic salts and mercury compounds being ingested or coming into contact with the skin. Do not come into contact with parts that are under high voltage. Persons with active electronic implants (e.g. heart pacemakers) must never work on HID headlamps. Wear insulated safety shoes, safety glasses and protective gloves. Remove flammable materials and ensure sufficient ventilation in the working area.
NOTE: When diagnosing the exterior lighting circuits, remember that high generator output can burn out bulbs rapidly and repeatedly; and, that dim or flickering bulbs can be caused by low generator output or poor battery condition. If one of these symptoms is a problem on the vehicle, be certain to diagnose the battery and charging system, then repair as necessary.
NOTE: A good ground is necessary for proper lighting operation. If a lighting problem is being diagnosed that involves multiple symptoms, systems, or components, the problem can often be traced to a loose, corroded, or open ground.
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 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
BRAKE LAMPS
NOTE: The rear lamp units and the CHMSL are illuminated by several LED units that are soldered to the electronic circuit boards within the lamp housings. The brake lamps are powered by high side drivers within the BCM based upon an input to the CAB from the brake pedal position sensor. If all of the LED units within the CHMSL fail to operate, diagnose and repair the brake lamps before attempting to repair the CHMSL. If the brake lamp LED units in the rear lamps operate but none of the CHMSL LED units illuminate, test and repair the CHMSL ground or feed circuit if required. If some of the rear lamp or CHMSL LED units operate and others do not, the outer rear lamp or CHMSL assembly must be replaced with a new unit.
DAYTIME RUNNING LAMPS
FRONT FOG LAMPS
HAZARD WARNING LAMPS
NOTE: The hazard switch is integral to the instrument panel switch bank, which provides a hard wired output to the BCM. Before performing any of the following tests, confirm whether the left and right turn signals operate satisfactorily. Then determine whether the other functions of the instrument panel switch bank are operational. If the turn signals are ineffective or operate improperly, or if the other instrument panel switch bank functions are ineffective, diagnose and repair those problems before attempting to repair the hazard warning lamps system.
HEADLAMPS
NOTE: As part of the exterior lighting failsafe feature, upon ignition ON all exterior park lamps and the headlamp low beams will illuminate regardless of the headlamp switch control knob position if the IC cannot detect an input from the headlamp switch, or if there is a loss of communication between the multi-function switch/SCM and the BCM. Diagnose and repair those problems before attempting to repair the headlamps. In addition, the BCM will store a DTC for an open or shorted headlamp circuit.
PARK LAMPS
NOTE: As part of the exterior lighting failsafe feature, upon ignition ON all exterior park lamps and the headlamp low beams will illuminate regardless of the headlamp switch control knob position if the IC cannot detect an input from the headlamp switch, or if there is a loss of communication between the multi-function switch/SCM and the BCM. Diagnose and repair those problems before attempting to repair the Park Lamps. In addition, the BCM will store a DTC for an open or shorted park lamps circuit.
SMARTBEAM(R)
NOTE: For SmartBeam(R) to operate, the Auto High Beam option must be enabled using the customer programmable features function of the Electronic Vehicle Information Center (EVIC). Also, the BCM must be properly configured for the automatic headlamps option using a diagnostic scan tool. Refer to the appropriate diagnostic information.
TURN SIGNAL LAMPS
NOTE: The turn signal switch is integral to the multi-function switch/SCM, which communicates with the BCM over the CAN data bus. Before performing any of the following tests, determine whether the other functions of the multi-function switch/SCM are operational. If the other multi-function switch/SCM functions are ineffective, diagnose and repair that problem before attempting to repair the Turn Signal Lamps.
