The security light is flashing. Truck won't start, turns over but doesn't fire to the coil packs. Replaced right side exhaust manifold and #1 and #3 coils packs and installed new battery. Could it be the key or what?
V8 5.4l 4 wd
It could be the key or the security module. What happened before the truck quit running? It may be that the security system needs to relearn, this requires the proper scan tool to that. Do you have the means of code reading the security system? What have you checked so far?