Rewiring The PATS System:
Both the explorer and the ranger have a different style of PATS system, rewiring is necessary to fix this.
the explorer has PATS type “B”, under this system, the key sends a signal to the PATS transceiver, the transceiver then sends a signal to the PATS transponder (PATS module), and this then sends a signal to the PCM that tells it that its ok to run. For a type “B” system, if the PCM does not receive the “ok to run” signal from the PATS module, then it will still allow the motor to crank, but it will not send pulses to the injectors cutting all fuel.
Starting in 2001, the rangers began using the PATS type “E” system. The way that type “E” PATS is different is that it eliminates the PATS module (transponder) by integrating it into the PCM. Under a type “E” system, the coded keys send a signal to the PATS transceiver, the transceiver then takes the signal and sends it directly to the PCM where it checks to make sure that the key code is correct and then allows the motor to run. Under the type “E” system, if the PCM fails to detect the properly coded key, then it will do two things. First, it will not send pulses to the injectors to cut fuel to the motor. Secondly, the type “E” system has the starter solenoid grounded in the PCM, if it doesn’t receive the proper signal it will not ground the starter solenoid which keeps the motor from cranking when the ignition is turned.
Obviously, because we are using the PCM from an explorer with a ranger body harness, when you do the swap he PCM will be looking for a signal from a module that doesn’t exist. When you have the motor in the truck and you excitedly turn the key for the first time not only will it not crank (because the starter solenoid isn’t grounded), but even once you do ground the solenoid and get it to crank, it won’t fire because the injector aren’t firing.
To fix this, an Explorer PATS module must be wired into the truck. This will require a different transceiver and key because the two different PATS types use different transceivers and keys

If you swap in the PATS from the Explorer, you'll be set. If you use your existing PATS (key's etc) you'll have to tow your Ranger to a Ford dealer to re-program PATS to synch EEC, PATS module, and Keys.

The 1999-2001 Explorer PATS is 100% compatible with a 1999-2000 V6 Ranger. If the Explorer PATS module and keys are also transplanted to the Ranger, they should work immediately with the Explorer PCM. If the original Ranger PATS module and keys are reused with the Explorer PCM, a dealer would have to "introduce" the new parts to each other before the engine could start.

Type B (1999-2000 Ranger & 1998-2001 Explorer): Under the type B system, the key sends a signal to the PATS transceiver, the transceiver then sends a signal to the PATS transponder (PATS module), and this then sends a signal to the PCM that tells it that its ok to run. For a type “B” system, if the PCM does not receive the “ok to run” signal from the PATS module, then it will still allow the motor to crank, but it will not send pulses to the injectors cutting all fuel.