I am swapping a 1999 3.0 v6 for a 2000 4.0v6 engine. The switch will not start the engine. The switch shows a theft light. I have changed out the computer and the coil pack.
Is there something more I need to do to make this work?

Thanks for your help

 

Welcome to the site


1999 and 2000 Rangers both used Type B PATS, PATS = passive anti-theft system, passive means no horn or siren will go off.
PATS can disable starter motor on some years, but disables fuel system on all years if correct PATS key ID is not seen when starting engine.
So while starter motor may not be working, fuel system will also not be working if PATS is the problem.

When you turn on the key in a PATS vehicle, the key slot will read the PATS key's ID tag(no battery needed in the key), this tag number is sent to the PATS system where it is compared to 3 or 4 tag numbers that were programmed into the system at the factory, if tag number match is found then computer "allows" engine to start.

in 1999/2000 there will be a PATS module above the Glove Box that is programmed with the "allowed" PATS keys at the factory, it is also connected to the computer.
(in 2001 rangers got type E, PATS module was in the computer)

This PATS module and the PCM(computer) are "married" at the factory, they can not be swapped separately.
A Ford Dealer can "remarry" PATS module and PCM, if either fails and a new one is needed, but only a Ford Dealer can do that.

So you need to get the 4.0l computer's matching PATS module and a working key for it, and swap it for the 3.0ls PATS module, and then have the ignition cylinder rekeyed for that key.
Or after swapping out the PATS module have a mobile Locksmith with PATS software come out and add your 3.0l Ranger PATS keys to the 4.0ls PATS module.
Locksmiths with the proper software can add keys to PATS memory, but they can not "marry" module and computer, thats a Ford Only task.

OR..........you could pay a programmer to remove the PATS check on the 2000 4.0l computer.

OR tow vehicle to Ford Dealer and have them remarry 3.0l module and 4.0l computer, this can only be done in the vehicle, they can not marry computer and module for later install.

 

If you can get the pats module and a key for the computer you installed. You can put a key inside the steering column next to the antenna wire and use your old key. Of course, you will no longer have the pats protection.