Diagnosis gone wrong no start Ford Expedition
The story of wrong diagnosis 2002 Ford Expedition cranks no start. A mobile mechanic tows in a vehicle says he thought it was the fuel pump and replaced the fuel pump. We first check for a spark and pulse and saw no spark or injector pulse.We then checked the inertia switch and fuel pressure fuel pressure was 0 psi. We then changed the crank shaft position sensor, we now had spark but no injector pulse. While cranking we noticed the theft lite flickering.
If the PATS system passive anti theft system is good–it should flash every 2 seconds in off–turn on for about 3 seconds when turned to run/start.it should then go off while cranking. The problem with the vehicle was the ignition key that had gone bad, replacing the key with a programmed key was the answer. Lesson learned is to make sure the PATS system needs to be checked before any other diagnostics.