2007 Mustang GT

Hi,
Have a flashing security light when Key On?
Did you bypass the neutral safety switch?
The car recognizes the Auto Trans key & eec, this is why it starts.
The new EEC still thinks it’s in the vehicle it was taken from,, the correct VIN# and has no idea why keys it doesn’t know are being run
I’m are not those paired to it. Sounds like it, therefore, Welcome to PATS! Let’s be more certain that it is PATS.
This FOB programming has nothing to do with PATS, it’s one entity & cannot be bypassed, worst case, a dealer or mobile PATS trained locksmith.
if that occurs- get 2+ made, prices are less.
This is not a no Crank, it’s turning over- not starting, correct?
Other reasons for “no start” the fuel pump priming with key on, have another listen at the pump while another’s cranking over- is the pump running while actively attempting to start the car?
You need to view & pull your codes from the EEC, what are they?... 1260
If it disallows codes to be pulled, try this..
Disconnect the battery cables, let the car sit for 5 Min’s, reconnect cables & it should let you pull codes, jot any others down, clear them, retry starting. 1221..
As there’s bound to be more “barriers”, as you move forward, some good Data:


Post what you find,
Best!
John