Service function guideLighting Fault Diagnosis

This guide delivers a complete, professional workflow for diagnosing lighting faults on modern vehicles, covering conventional bulbs, light-emitting diode (LED) assemblies, and the control modules that govern them. It is written for working mechanics and experienced DIY owners who already understand basic electrical testing and want a structured method that avoids parts-swapping. You will learn how to read the lighting circuit logically, from power and ground to module communication, and how to isolate a failed bulb, a damaged harness, or a faulty control unit with confidence. By the end, you will be able to perform a full lighting fault diagnosis, verify the repair, and hand the vehicle back with the system operating exactly as the manufacturer intended.