So, it only really seems to do it when its cooler/cold outside, but I'll start my truck and then it will(what appears to me to be a short) just shut EVERYTHING electrical off, no gauges, no security light, no dome light, no power locks, absolutely no power. So I pop the hood, and go wiggle the loomed set of wires coming out of the bottom of the red box that the alternator runs too, and then everything will come back on and sometimes I can start my truck and then sometimes it just repeats the whole process. When the truck does start it wont idle and I have to feather the gas to keep it going.

I checked the ground on the back of the block, and the one on the head both were fine, battery connections are good. I'm just getting frustrated with it so I'm probably overlooking something simple. Any ideas would help, thanks in advance.

 

check the ground to the block right behind the power steering pump/resivoir. mine did all kinds of crazy stuff because i missed that ground. there will be two ground wires there

 

Just went and checked that after I saw your reply, that one is good as well. Thanks for the suggestion, I'm just stumped.

 

The only thing that really confuses me is why temperature causes it. If my truck is warmed up and the engine bay is hot, or it is over like 55 outside it won't do it. Also, its never done this in the winter before. I asked my father about it and he said maybe its my computer itself having a problem with cold temps. Because this isn't my original computer core. I had Nelson re-tune my truck not too long ago, so this is a new core, and he said maybe this computer had a problem reacting to cold temps and Nelson didn't catch it because it works fine in warmer temps. Anyone had an issue with this before, or heard of something like that?

 

i still think its a loose or bad ground. sounds like the main ground from the battery. did you check the connectors on the pcm to make sure they were tight? evrything is tight coming from the alternator into the junction box?

i have never heard of a pcm acting funny because of temperature change.sounds like maybe theres a short somewhere in the loom between the battery ground and the main ground on the block. temperature change could be a factor here. everything contracts when its cold causing a bad connection, and expands when its warmer causing a better connection.

 

What year is the truck?
Any other electrical system mods?

First step check your battery!!! Trash in equal’s trash out, voltage is not always a guarantee the battery is optimal, would require a full charging system & load test to verify. Cooler weather really hurts the older battery's (what type of battery do you have? age of the battery as well? that being said.

Please use a DDM to verify voltage for any steps below:
I would check the side post terminal connections and cables. GMs old side post design has some serious flaws. Don't just check if they are tight, pull them off and peel back the boots carefully look for corrosion and double check the wire to connector, clean up if needed

Then check power & ground cables & connections to your fuse block

Then confirm the fuse block power by checking both the pre fuse side and then the load side of the circuit (could have an internal short/open inside the fuse block, there is metal panels inside it like a circuit board, and well when it’s cold it could separate enough to cause an open circuit. obviously check when the short/open occurs when it’s cold.

 

^^X2 Had the same thing happen on my wifes previous ride. Everything went ape **** all due to an old battery. Easily overlooked..