Pats question

[cp2295]

So I swapped my 99 3.0 for a 98 4.0. The new PCM is a 98. Anyways my old key still works but the theft light flashes for about the first 5 minutes of driving then goes away. I figured a steel key would work now, but when I tried it nothing would happen, no crank or anything. I used my 3.0s wire harness, because the 4.0s harness did the same thing when I tried cranking it (with my chipped key). Did using my 3.0s harness bypass the need to go to ford? Can I save everyone $200 with that trick or did I just get lucky?

 

[Crossthreader]

When the PATS module recognizes a valid chipped key, it does two things. First it completes the circuit to the starter, then it grants permission to the PCM to allow the engine to run.

I suspect your 98 doesn't have PATS, so the PCM doesn't need permission to operate the engine. If you don't want to use the chipped key, just bypass the starter wiring to the PATS module.

 

[armadillon]

Living in a larger city, if I had the chipped key I think I'd stick with it.

 

[cp2295]

Oh yeah no I like having the chip, I was just kinda curious why after my engine swap I didn't have to go to the ford dealer to start the truck. So if I'm correct the pats module itself grants permission to crank the starter. Then the PCM grants permission to the fuel pump. Since the 98 never had pats it's not looking for a chip to grant permission to the fuel pump, but the module is making sure the starter won't crank.

So theoretically I could compression start my truck with the steel key right?

 

[adsm08]

More or less. IIRC the PCM disables the injectors, not the pump, but yes, you could pop start the engine with a non-PATS key if the need arose.