Check the ground on top of the bracket right by the alternator.

 

I have the plug plugged in and I thought that was the negative cable that I screwed in. Where exactly is the negative cable? I know there is two cables to hook into the alternator. Both are hooked in.

 

Should be to little ring terminals on the alt itself, and then a ground strap that goes the bolt that holds the A/C lines in place, on the bracket. And of course, the fat wire that goes to the PDC..... There's pics in the service manual. (if you don't have one, get one here.)

 

Alright, I dug a little deeper. Pulled the alternator and battery and got them tested. Both are good. The truck will run just fine for about 60 seconds, and then my voltage gauge will decide to drop pretty fast. My check engine light has always been on but I figured I should go ahead and see if there were any new codes.

P 0601
P 1682
P 0622
P 0443
P 1495

I know the last two are EVAP stuff, but the other ones make me really nervous. I don't think it could be a bad computer, but who knows. I need to find where I am losing voltage and have no idea where to check. Anyone have any ideas?

Thank you guys a ton for helping me out.

 

When you got your alternator tested, did they run it for more than 60 seconds? I ask, as some will test it really quick and assume it's fine if it puts out adequate voltage.

 

P0601 PCM Internal Ctrller Failure

That one right there is a killer. The PCM itself is failing.

Reset codes, and see if that one comes back. If it does, need to replace the PCM.