If you run into an electrical problem with your GMC, you may want to take a moment and check a few things out for yourself. Before you dive in with a multi-meter, you will want to obtain a free wiring diagram for your specific model. You may need to locate a specific color wire and its exact location. This is tough to do without a wiring diagram to help guide you through your diagnostic procedure. Find the free GMC wiring diagram you need and get started repairing your GMC electrical problems.