How does the PATS system prevent the truck from starting?

 

There's a chip in the key that has to be programmed to match the reciever in the vehicle to tell it the "driver" is legit. Otherwise, no start. Key may work fine but the PATS is the boss! Does your '01 have PATS? I had a '99 and an '02 but I don't even remember if either had it. I think they became more complicated after the '04 NB.

 

See owner's manual for complete description of the Securilock (PATS) system.

Basically, if the code read from the key does not match one already programmed into the vehicle's system, engine operation is inhibited by preventing the injectors from operating.

PATS was first used in the 97 SUVs, 99 F150 trucks, much later in the SD lineup.

 

Does it turn off the cpu or fuel or what? I
have a 01. Thieft light is all of the time. Engine will crank over but not start. It will start with starter
fluid sprayed into air cleaner.

 

No. The computer's software prevents the injectors from operating when PATS is triggered.