Re-posting on the Distress Board!

So here's a little background on this truck:
I bought it from a mom and pop dealership with a 1 year warranty. 3 days after the purchase, I start noticing electrical issues (extremely dim headlights, cab lights coming on and off, needs jump to start). Obviously the first assumption was a shot alternator which is covered by the warranty. We take it to the shop and try TWO brand new alternators and neither of them take which points to more serious electrical issues.

Diesel mechanic says it needs a new wiring harness (NOT covered by warranty - we demand the dealership to pay half since it is less than a week after the purchase). We get the truck back (after about 2 weeks - slowest mechanic ever) and it drives fine for a couple of days.

I have a diesel mechanic at work check it over just to make sure it's good to go - he checks EVERYTHING including the injectors which he says are firing beautifully. No codes were popping up on the ECM.

We take our pretty new truck for a family dinner with my 4 year old in the truck and BAM the truck dies at 60 MPH and we get rear ended and completely total this poor foreigners pontiac. He doesn't have insurance and speeds off before the cops show up.

The truck would no longer start, gauges were not reading what-so-ever. Everyone concludes the ECM must be shot so we take it to get rebuilt (there goes another $700). We pop the ECM back in a week later and it starts up BEAUTIFULLY. Let it run to warm up and it kills itself but starts right back up afterwards - we notice some smoke coming from somewhere (it was too windy to tell from where).

We scan the ECM and get the following codes: 1652, 2509, 336. We clear the ECM, drive it around the block, and scan it again and only get two codes: 541 & 521. Truck wants to run rough, idle rough, and now there is a KNOCKING in the engine that was never there before.

We are completely stumped at this point. Could the ECM have been flashed wrong? Is this something more serious? Is it possible that the original wiring harness "fix" wasn't fixed correctly?

Any suggestions are appreciated! Sorry for the LONG story.

UPDATE: all grounds have been checked and cleaned & still having all of these issues. We dropped off the ECM to get re-programmed and will see if that will help but I would still really appreciate any additional suggestions!

 

I'd be looking for places where the wiring harness may be chafing on metal parts. May have a major B+ or 5v being grounded out intermittently, and they're sometimes very difficult to locate. I've had a few nasty issues like that before.