Diagnosis And Testing: Notes
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.
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.
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.
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 hardwired 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, details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds. For proper wire repair, and connector repair procedures. Refer to CIRCUIT TESTING PROCEDURES or REMOVAL or INSTALLATION .
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.