Custom 6.0 Sierra electrical and idle issues
 

The truck is a 2008 Gmc sierra that came with a 5.3 and 4l60. It has sense been built into an offroad truck with a ton of fabrication. I swapped a custom built 6.0 with a 4l80 into it within the last few weeks and now im having a few different problems.

Motor info, custom cam motions cam, 3 angle valve job, cnc ported heads, stroked to 408ci, custom pistons, etc. Runs a Truck style intake, bigger injectors, Has a ginormous air filter before the maf, trans is a full reid case , 300m shafts, 5 pinion planeteries, all the good stuff with a 3200 stall converter.

The truck had a base tune put on it, and tcm flashed for new trans through an extremely reputable gm guy who has tuned a ton of the same motors from the same motor builder.

1. The idle is great, I start it and it runs perfect; however, if I tap the throttle it revs up to 2500rpm and won't come down till I shut the truck off. Never slows down or slowly comes down. If I put my foot on the throttle it wont go above 3k either.

2. My truck has a CBR radiator running spal electric fans. They are wired into the factory plug and harness of my factory fans. The right fan comes on at 220-230 and left fan wont come on at all. I turned ac on and left wont come on still. ( These fans work whether they're wired correct polarity or not, reverse polarity just means they spin other direction ). Got all new fan relays, chased all grounds, still same problem.

3. My headlights.. When you use the key fob, they flash. At first the left one wouldnt flash but the lights worked if the truck was running. Nowit has turned into the right one wouldn't flash. now neither flash but both work?

Harness has been repinned for trans, all done professionally, all grounds are hooked up ( except the one that goes from firewall to hood because I don't have a hood light anymore.), the tune is straight forward and near a "factory" tune for trans and a predone tune for a similar motor he did.

The truck has been waiting on a driveshaft for a few weeks now, and I just got it. I'm hoping to move the thing this weekend. But my problem is my converter is a 3200 stall, and it wont go above 2k, i don't want to damage anything, and I cant even get it on a trailer like this. I also looked into a tech II scanner, but people are saying it will delete the tune on the truck for a throttle body reset? I tried unplugging battery and doing the basic reset nonsense already, no luck

I got in contact with someone at the dealer and they ran diagrams, said that my left fan and headlight are connected to the same ground, and right headlight and fan are same ground. They both run off same ground for low speed from 210 to 230, and then the ecu sends a signal to independently ground for high speed. So fans and headlights are related to eachother, for some reason the truck is skipping lowspeed and going straight to highspeed and only the right not left as well. As for throttle body, i'm trying to get my hands on a tech II scanner, no luck so far.

Update,

I was waiting on a driveshaft to see if it would move. I built my carrier bearing mount and got everything plugged in last night. Put it in drive, and the truck refused to move. Plugged in a tech II scanner, says its going into 2nd gear at all times. BUt it did rev normal like its supposed too. I pulled battery and let it sit, replugged in and the truck would barely start, was starving for fuel. Asked my trans guy this morning and he had me unplug the round plug on the side of the trans and see if it moves and it sure did. So now it sounds like a wire thing? i moved pin 45 to pin 26 on tcm side and used a plug and play harness adapter on trans side.. still haven't figured out headlight or fans yet though.