Sierra 5.3 w/4L80e swap. Alt wont command charge....

[GN_Drake]

Just got the truck back from swapping 4.8 to 5.3 with 4L80E. Shop stated the segment swap for 80e wouldnt work, so they did an entire write for the 1500HD file instead to get the 80e to work.

Shortly after, they called to say the new alt I had on wasnt charging. No big deal, I grab a new delphi while on my way to get the truck, and swap it in before leaving. About 30min down the road I noticed the voltage dropping under 12, 11, 10, then down to 9 when everything shut off except the engine.... few seconds later, BAM the alt charges once I stop the truck.

Now, how do I figure out where this signal is sent in the PCM. It has to be related to the tune, as two alts are not the culprit. I am taking the old (new) alt to get tested today, but looking to understand what my options are. Just spent a ton of $$$ getting the work done, and anxious to get out and drive the damn thing. Shop is 100mi away, so I am working with them remotely to try to T/S as well.

I am updating my HPT to 4.0, as I was still on the OLDDDD OS trying to hold out as long as i could. Will post log after.

[kingtal0n]

heres what I have for the '411' truck PCM (red/Blue) 02~

alternatorfinal.jpg

The wiring is on "lt1swap.com" also for others

[GN_Drake]

Found the issue to be a loose positive terminal.