Headlamp: Testing and Inspection

HIGH INTENSITY DISCHARGE HEADLAMPS

The High Intensity Discharge (HID) headlamps are supplied B+ voltage and ground, the same as normal halogen low beam lamps. The low beam system is different from there forward. The ballast module is mounted to the inside of the headlamp unit access cover. The ballast module has internal circuit protection to prevent module damage in case of an open or shorted circuit. The module has overcharge and undercharge circuit protection. If either is sensed, the module will not illuminate the headlamps for that key cycle or until the fault is corrected. Recycle the ignition and headlamp switch if both headlamps do not illuminate and the fuse is OK. Before determining the headlamp assembly is faulty, check the connector at the headlamp and the low beam fuse in the Power Distribution Center (PDC). Check the BCM for any faults on the park, high beam AND fog lamp outputs and the low beam relay coil. If the BCM senses any short conditions, it will disable these outputs until the next ignition On/Off cycle. If the ballast module senses a short or open circuit condition, it will not operate the lamp/igniter.

The headlamp unit assembly must be removed to perform the following tests Headlamp Unit - Removal.

1. Inspect lamp/igniter assembly for a burned out lamp. If lamp is burned out it will appear black or smoky, similar to a normal halogen bulb. If lamp looks OK, go to 2.
2. Check for B+ battery voltage at the two pin connector going into the ballast module. Refer to Wiring Diagrams for connector location. If battery voltage and a good ground are present, go to 3. If B+ voltage and a good ground are not present, refer to Wiring Diagrams for circuit and connector locations to find short or open circuit.

CAUTION: The Ballast Module and Lamp/Igniter are specifically designed for each individual application, When replacing either the Ballast Module or Lamp/Igniter, make sure they are compatible with each other. Check with the parts department for compatibility.

3. Plug in a known good ballast module and check for lamp operation. If lamp lights, replace ballast module. If lamp still fails to light, replace lamp/igniter assembly.