Thinking I've got the wiring all figured out I decide it's time to hook the battery up and test some things out. As I go to connect the terminal the horn starts blaring. Try the power locks, nothing. Turn the key to on, try the power windows, again nothing. At some point in this series of tests the ABS unit spins over as well. Plug in the headlight switch, no interior lights with the door open, no HVAC blower, no radio. At this point the list of things that work in the cab is probably shorter than the list that doesn't.
I'm feeling pretty overwhelmed and deflated.
I'm back to this forum asking for help.
https://www.gmt400.com/threads/who’s-crazy-idea-was-this-1995-1996-cc-wiring-diagram.45023/#post-1051740
I try comparing the wiring diagrams from '95 to '98. I've never really tried to understand GM wiring diagrams before. I don't know about you, but I struggle. I kind of got it now, but that's after weeks of staring at them. Feeling like I am going to have to abandon the idea of using the '95 cab wiring I start hunting for alternatives. The closest thing I can find is a '99 Suburban not too far from me. I connect with the guy and he is kind enough to let me have the cab crossover harness out of his Suburban in exchange for my time in helping him disassemble some of the dash parts. He also let me have the PCM/ABS mounting bracket that I learned is not the same as the ABS/Washer Fluid bottle in '95 (they're really close looking which is why I didn't save the '00 bracket). It's like they tried to make it the same, but somehow screwed up when it came time to build the '96's. Anyway, he was a great guy and I was very thankful. My thought in getting the Suburban harness is I'd have enough to be able to build my own '00 crew cab pickup harness between everything I had. The biggest discovery I had when removing the Suburban harness was that there was a ground lug over on the passenger side that my '95 didn't have! I landed that ground terminal on an insufficient ground when I installed the '00 dash! When I got home I moved that terminal over to a solid grounding point on the cab and more things started to work, particularity the blower, HVAC, radio sound. I still had no illumination on the radio itself.
More staring at the wiring diagrams and more probing wires between the '95 dash and the '00 dash. What I needed to make the windows and locks work was another ground. Once I connected the ground coming from the door wiring to the instrument panel ground all the power door stuff started working.
Down to just the interior lights not working when the door jamb switch activates (but they do work with the over ride on the dimmer), the horn still going, and the radio not illuminating I decide it's time to see if the engine will run.
Turn the key, it cranks.....and cranks....and cranks....nothing.