LS Swapped 86 C10 DBW issue

[shortboxin]

I had bought and installed a Chinese standalone harness, so I figured I better be on the safe side and I spent 12 hours checking the PCM harness for shorts and opens. Found 6 wires that were in the wrong locations. Got them moved around and started up the truck.

Started right up and after I got oil pressure, I hit the gas. It accelerated normally the first and second times, but after that, nothing. Pedal was dead. Checked codes and found that I had a U0107 (lost communication with TAC). Reset code and again it would rev 1-2x and the same thing.

I noticed when I was checking the harness, that pin 12 to pin 13 of the TAC was shorted. When I unplugged C1 from the TAC, there was no short at the pins on the PCM. Checked continuity from pin 12 to pin 13 of the TAC when removed from the vehicle and it's a direct short.

Is this normal? Seems unlikely to me, but I've never done a DBW LS swap before, only DBC. Any help is appreciated greatly!

 

[TotalyHucked]

I don't have any experience dealing with TAC modules other than what my tuner buddy has told me, but it's very possible your TAC module is dead/dying. He had to replace one in my coworker's truck not long ago

 

[shortboxin]

I don't have any experience dealing with TAC modules other than what my tuner buddy has told me, but it's very possible your TAC module is dead/dying. He had to replace one in my coworker's truck not long ago

Thank you for responding. I've been waiting on the edge of my seat overnight on this since I really want to get this out of my garage today (actually my wife wants it). It's been taking space for 6 weeks now.

My neighbor has a 2006 C10, so I think I'm going to hit him up to see if I can check pin 12 to 13 to see if they are shorted. I should've mentioned last night that these are the serial communications pins to the PCM.

Another thing I just found out is that the guy I bought the 2004 Silverado 4.8 from sold me a 2006-2007 pedal and TAC module. The TAC pinouts appear to be the same from what I've found online, but I started to wonder if the bitstream FROM/TO the PCM may be different. There's got to be a reason that the TAC is different between 2004-2005 and 2006-2007 and maybe that's it. It is a communication issue, so I'm going to look into this further as well.