Originally Posted by
bignick
Got it figured out. And I'll post below what the fix was for anyone else with the issue.
So did some research. Found some of the info on this forum.
So my swap came out of a 2011 3500 express cut away van / box truck.
E38 trucks / van use the ac control head panel to send a message via the canbus to the ecm to control the fans and compressor. Camaros and CTSVs do not. I tried everything I could think of. Segment swap didn't work. I made sure everything was working. Back probed all of the wires in the system. 5v ref from ecm was working. Had a good ground. Jumping the switch sent the voltage back to the ecm. Hptuners, EFI Live and a gm dealership scan tool / laptop would not read any information. No voltage and no pressure.
So I had Geoff at EPS clone my ecm file and wipe another known good E38 ecm and copy my file over. Still the same results.
Went back to my tuner (Justin @ Asylum in Baton Rouge) we had been talking ever since the swap was done back in May about how to get the damn thing to work. I was really loosing hope as he told me he's never gotten one to work. I told him, I'll be the one to figure it out. I'm no tuner, but I'm a damn good troubleshooter. He devoted a morning to troubleshooting and trying to figure it out. He started over with a silverado vin and still nothing. I left him alone and let him do his this.
An idea popped into my head. So I walked into his office and told him about the ac request setup in a Camaro and how it was different from a truck. Asked him if he wouldn't mind pulling a e38 ecm out of another car, plugging it into my truck and we just "key on" the truck and not start it and scan it and see if it reads the AC pressure voltage and pressure .BAM!!!!!!, worked instantly. We had a solution.
So Justin spent some time, finding me a compatible OS for the E38 that would also be compatible with my 6L90e, y'all know. It's all got to work together. Lucky for me I was already using a camaro accelerator pedal, throttle body and maf. So that made it even more compatible with the Camaro OS.
I picked up the ECM last night. Got it home and done! Worked. Sat in my driveway and verified function with HP tuners. Now I can turn my AC on and the transducer will control the electric fans when the ac compressor head pressure creeps up and keeps the relief valve from blowing all my refrigerant out.
So short version:
E38 truck / van OS wouldn't read ac transducer.
Swapped to a camaro OS comparable with my transmission and E38. Now ac transducer functions as it should.
--Side note - the camaro OS requires you use a camaro accelerator pedal.
Shoot me a message if you need any help or have questions.