In an '02 it's actually more likely to be fuse #30 (the fuel heater) but, if you've checked the PCM plug for power & ground, that too isn't going to be it...
BUT, if the IDM relay doesn't energize, AND you can't communicate with a New PCM either, you've got something really weird going on. I agree, it has nothing to do with a GPR (which you don't even Need over 40*).
What are you using for a scanner? (the generic OBD-II aren't of much use with these engines but it certainly should communicate). I'd wonder about the OBD-II port but you say the WTS never shuts off. That's a sign that the PCM is really confused, it shouldn't ever do that.
On one hand I'd be thinking this is all a computer or electrical issue (the WTS, Communication problem, intermittently working again, then not) But, it sure would be nice to confirm you had HPOP/Fuel/Oil pressures and that the injectors were getting signal to fire. All of which we rely on the scanner for but, I guess, could be confirmed, mechanically, with out it.
On the electrical side, does everything look solid? Body Grounds too? How about the fuseable link connection? (POTENTIAL ELECTRICAL CORROSION if your truck is like mine......
You've got your hands full
The fact that, after one of the GPR changes, it worked for a while would drive me crazy!