How are Headlamp Control Module issues diagnosed?
Unless a vehicle is displaying a diagnostic trouble code, either as a warning light on the dashboard or by way of a special scan tool, a technician will have to rely on a process of elimination to diagnose a faulty light control module. Many of the symptoms of a bad LCM (or other module) can be attributed to other causes. Intermittent headlights can be caused by a corroded ground at the wire harness. Rapidly blinking turn signals can be a result of a burned out bulb. Starting with the fuses, relays, and bulbs, a technician will rule out the simplest and most common lighting failures first. A series of tests for voltage and resistance with a multimeter will help to locate problems with the wiring or the connections in the system. A qualified technician is skilled at pinpointing a specific problem, targeting the electrical circuit where the problem presents itself, and honing in on the root cause of the problem. Special knowledge, tools, and vehicle-specific information is necessary for proper diagnosis.
How are Headlamp Control Modules replaced?
Accurate diagnosis is usually the most difficult part of light control module replacement. The procedure for replacing a module is specific to each vehicle because it can be located in a number of places. An LCM is usually located below the steering wheel in the lower dashboard, but it can be located elsewhere: behind the glovebox or in the engine compartment near the fuse block or on the firewall. Other modules that control specific adaptive headlamp functions, such as auto-dimming, auto-leveling, and auto-tuning functions, may be mounted on the headlamp assembly along with the HID igniter module. Disconnecting and removing an old module, and replacing it with a new one, is a matter of unplugging the old and plugging in the new. It is not complex. Accessing the module may be a different story. If the module is located in the dashboard, interior trim panels will need to be disassembled. If the module is mounted on the headlamp, the headlamp assembly - and likely other components - will need to be removed. Again, vehicle-specific repair information is essential. And the new module will probably need to be programmed before it will work.