Star unplugging anything that runs off the 5 volt circuit and anything the PCM powers up. Cam, Crank, Coolant temp, TPS, MAP, AC High sid press. switch, Purge solenoid. Unplug them one at a time then check your communication. Reboot the scan tool each time. Don't expect it to just come alive you will get thrown off the trail. I would start with the crank sensor. Make sure no wires are melted and touching up under the truck. You know, the O2 sensors, range switch speed sensor in the trans and on the rear diff. The tranfer case pigtails (they are there on 2WD also) If these things have an internal short it will take out your PCM comm and maybe even kill your PCM in some rare cases. I had one recently that was killing PCM due to the tranfer case range switch dummy pigtail shorting 12V straight to gorund.

 

OK, so by a very very slow long and drawn out process of elimination and doing test about eight more time then I probably should have needed too, I have come up with this. Testing "sensor ground wire" for bleed over voltage, key in "ON" position. unplugged every sensor I could find, slowly worked through them. Now all sensors plugged back in, except battery temp sensor, and vss. If I plug the vss in, I get a 3.5 volt reading on my sensor ground. unplug the vss, I get a .002 or .003 which I am assuming is O.K. vss unplugged, plug in the battery temp sensor, I get a 1.35 volt reading on sensor ground. I am assuming that either one of these would be enough of a short to put my pcm into a shut down mode. Still not able to get an ohm reading between ground, A31 or A32 and 5 volt primary. Assuming I will not be able to until I can complete circuits. Does this sound like I am going about this the right way. or should I be towing this thing to "Anchorage auto electric" because I know I am in way over my skill level. Thx again soooo much for your help TNtech.

 

I am chasing a similar short in my Grand Caravan. This sound like a huge committment.