Jsully72

Thanks for all your help with Mike. I was able to check the resistance on all the wires today and everything looks good there. I checked all the ccd through the gauge cluster, pcm, and ecm. Same with the sci. Everything there looked good with the only assumption that I shouldn’t have anything at the sci bus on d20 since I have a diesel. (The wiring is there. ) All of my power and grounds are correct and the voltages are correct at the ccd pins on the obd port. I was able to borrow a 2001 pcm from a buddy today and swapped out real quick to no avail. My code reader lights up but no communication. Any ideas? Thank you, Jim

I just checked the voltage at these wires and the voltages are correct. Any ideas where to check from here? Thank you, Jim

Ok, a little backstory- the truck has a build date of 8/99, auto 2500 with 370k miles I bought this truck recently with a bad transmission but had a reman in the bed. I dropped the reman off at a tranny shop to have them check it out and picked up a single disc torque converter while I had it out. The tranny checked out ok so I swapped the transmissions. On initial install, I only had 1,2,3 shifts with no od and no lockup. I dropped the pans on both and noticed the pressure sensors were different. I swapped the od solenoid, pressure sensor, and wiring harness from the original tranny to my new transmission. By doing so, I was able to pick up od and lockup but not it will not downshift from 3rd gear unless I do it manually. I bring it to the tranny shop to have them read the pressures and figure out what’s going on before I just start throwing parts at it. They were never able to get the scanner to read anything from the obd port. This brings me to my current issue. I have power and grounds on the port. I checked resistance and the violet and blk/white wires from the cluster to the pcm and they all check out good. I’m stumped as to where to go from here. The reason I bring up both issues is I’m wondering if they could be related? I’m leaning towards the pcm being bad but I don’t want to just throw one at it and see what happens. Does anyone have anymore diagnosis tests for the obd port? Or any insight whatsoever? Thank you Jim