Where to start?

Question

Ok, fighting this thing for months. I bought a new module, programmed it, installed it, get the same no start as I did with old unit. I took the new one and reset. Reprogram and tried again and still nothing. I can't even get it to allow me to program the remotes to test the start function. So pulled it out, put the old one in and it tried to start after I pulled the OBD wire. Plugged it in and it started and ran for a few minutes and I tested everything. Great it works again...next morning, doesn't work. Single light flash and nothing. I started it with the key, did a remote start transfer and it took over. I pulled the key out and it stayed running for about a minute, then stopped. I tried again, nothing. So after 8 hours, I tried to remote start and it did, ran for about 10 seconds and shutdown. What's going on? Do I have a wire gremlin on the vehicle side? I disconnected all the harnesses wires, plugged them all back in and still nothing. Is there an alternative wiring?