Not really the PCM that controls that, NSS is a mechanical switch, when in Park or Neutral two wires on the NSS are connected, one wire from the ignition switch and the other wire goes to the Starter relay(motor), so when you turn the key to START position the 12volts goes out to NSS and passes thru to Starter Relay.
When shifter moved to Reverse or Drive, the two wires are no longer connected via the NSS, so a mechanical switch that slides to make and break contacts, like ignition switch does.
In the Power Box is the Fuel Pump Relay, pull it out, with key off, one of the slots in the socket should have 12volts, this is from the Fuel Pump Fuse, it has 12volts 24/7.
If no 12volts then check fuse.
Automotive relays have standard pin numbering.
Look here for diagram:
http://www.enginebasics.com/Engine Basics Root Folder/Automotive Relays.html
Pin 30 is the 12volt pin from fuse(fuel pump power)
Pin 87 will be connected to inertia switch wire(sends power to fuel pump)
You can use a Jumper wire from slot 30 to slot 87 and fuel pump should come on if wiring, and pump, is OK.
Pin 87a may or may not be there but it is not used in any case for this application.
Pins 85 and 86 are the control pins, with key on, either 85 or 86 slot will have 12volts now, this is the power for the relay, the other slot(not 12v) will be connected to the PCM, the PCM grounds this slot to activate the relay.
So the 12volts is on the whole time the key is, but there is no ground so relay stays OPEN, PCM grounds the relay to CLOSE it and send power(from pin 30 to 87) to fuel pump via inertia switch(located behind passenger side kick panel usually)
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