Hi PaulP38a,
I found your thread after running into similar issues as in your OP. It seems like the PCM ended up being the problem (outside of the no-crank issue)?
FYI, my symptoms are that my 2002 3.7 A/T Jeep Liberty Limited (in Canada) had a rough idle for a couple seconds on 3 occasions during the 6 weeks before the rough idle became consistent one evening. I am about to start checking wires, but I had coil codes on cylinder 1 and 2, and have found that cylinder 4 also isn’t firing in the troubleshooting process. Started with moving coil packs arounc and the problem didn’t follow the coil pack. Weird thing is that I am not getting spark on any of the plugs when I remove them (well-grounded when testing), but I am getting voltage to the 12V side of the pack. I just replaced the plugs yesterday with the the correct NGK ones (gapped properly too), but the rough idle is still there.
I’ll check the coil packs again and then move on to check grounds (power ground to PCM, engine and battery ground as BillWill said) and then wires.
The fact that it came and went 3 times before points to a common issue being the culprit. Just hope it is ground and not a wire (that I have to find) issue nor the PCM…