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.

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 CHMSL is illuminated by several LED units that are soldered to the electronic circuit board within the lamp housing. 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 the brake lamps and 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 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 CHMSL LED units operate and others do not, the CHMSL assembly must be replaced with a new unit.






DAYTIME RUNNING LAMPS

NOTE: Before performing the following tests, determine whether the headlamp low and high beams operate. If the headlamp low and high beams are also ineffective, diagnose and repair that problem before attempting to repair the DRL.






FRONT FOG LAMPS

NOTE: For vehicles in certain markets, the front fog lamps are designed to operate ONLY while the headlamp low beams are illuminated. If the headlamp low beams do not illuminate, diagnose and repair that problem before attempting to repair the front fog lamp system. Refer to the appropriate diagnostic information.






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/SAS 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.






HEADLAMP LEVELING





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/SAS 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.






REAR FOG LAMPS





TURN SIGNAL LAMPS

NOTE: The turn signal switch is integral to the multi-function switch/SCM, which communicates with the SAS over the LIN 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.