Any Ford Techs on here that can tell me the the purpose of the PCM power Diode in the Fuse Box under the Hood. Drove the truck in the shop put a set a brake pads on and when ready to test drive it would not start no fire no fuel pump on injectors pulse. After 3 hours of hunting and head scratching found the power diode burnt. put a jumper wire on it and cranked right up. Why is this Diode There "before" power goes to fuses and relays? Any Ideas what caused it to burn out. I've Never seen this before.