What is a Headlamp Control Module?
A headlamp control module (sometimes referred to as a Light Control Module or LCM) is an electronic control module, a computer, that coordinates the functions of the lights on a car, truck, or SUV. Some vehicles employ more than one module that control specific and complex functions: automatically dimming the headlights when oncoming traffic is present at night, leveling the headlamps to the contour of the road ahead, or turning the lamps to help visibility around corners. A vehicle with Xenon or High Intensity Discharge (HID) headlamps will also have separate igniter units mounted to each headlamp assembly that start and maintain an electrical arc that illuminates the bulbs. These units are sometimes called headlamp modules, or HID igniter modules.
How do Headlamp Control Modules work?
Whenever a driver turns on the headlamps (or other light) of a vehicle, a control module (LCM) sends signals to corresponding relays that switch the lamps on or off. There are many functions overseen by the LCM, including the high and low beam headlamps, the turn signals, the fog lamps, hazard lights, running lamps, brake lights, and even the dome lights. Some manufacturers install multiple computer modules to control more specific functions. A Daytime Running Lamp Module or an Adaptive Headlight Control Unit are examples of lighting modules with a narrower range of responsibilities.
What are the symptoms of a bad Headlamp Control Module?
Symptoms of a bad light control module are many and varied. Inoperative or intermittent headlamps, failing brake lights, problems with the turn signals, dash lights that don't work, or any lamps that blink too quickly are all examples of a faulty LCM. Just about any problem with the lights in or on a vehicle can be attributed to these modules. But most of the same problems can also be the results of other causes.
Can I drive with a bad Headlamp Control Module?