I've had my swap done for the most part for about a year. Now I'm finally putting A/C in my car. I'm looking at the 2 wiring diagrams that I have, but it seems to show conflicting information. I'm using the PCM from a 2004 Yukon and the wiring harness from a 2004 Express 2500.

I know that the LSx PCM need 12V into C2-17 (AC Request) to tell the PCM that you want AC. That grounds C2-43 (Clutch Relay Control), and provides power to the coil in the relay, switching it and sending power to the AC clutch. What I'm trying to figure out is how to integrate all that with my Impala's sensors. I had this figured out at one time, but those notes are long gone lol Any help would be greatly apreciated.

 

I was trying to figure this out myself a while back, but my wiring diagrams don't show any A/C request wires in a 2004 wiring harness. The A/C is controlled through the serial data line.

 

I got your PM on this.. I never hooked up any AC so I don't know it exactly, but I would line up the wires with the same name and go from there..

 

According to the schematics, on the 2004 Express 2500 (the harness I used) the AC Request Pin is C2-Pin 17.

 

This is good to know, there must be something different in the truck vs van program, because there is no C2-17 in a truck harness. So maybe I can have my PCM flashed to a van program, as long as I can keep my DBW. Are you using DBW or cable?

 

You're correct. There is no C2-17 in a truck harness. I just looked at my other one and veriified. I'm drive by cable. I'm running a Modified 04 GTO tune though. The Pin-outs for the 04 GTO list C2-17 also.