Bad BCM, ECM, or PCM?

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autigs3434

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2004 GMC Yukon SLT z-flex engine. Two weeks ago I replaced the valve cover on the driver's side. The thing was caked in sludge and oil. It's the only way to replace the pcv valve on my model. Ran the vehicle for a week and everything was fine. Last Saturday I was cleaning all of my cars and went to move this one out of the way, and it wouldn't start out of the blue. It was turning over just not starting. Smoke came out of the tail pipe once, windows have no power, can't unlock or lock doors, radio would not come on, the airbag and abs ight is on. When I tried to crank it a few more times it would just turn and act like it was about to crank but it never did. Noticed strong smelling fumes coming from tail pipe. Took both battery and alternator to the parts place and both tested good. All fuses look good and replaced the ones related to fuel pump and the modules, and I checked all of my grounds. Later that night, several hours later, I get home and notice my radio has come on all by itself without the key being in the ignition and I can't get it to turn off, so I end up having to take the face of the cd player off just to turn it off. The next day after charging my battery all night, went to crank it up and it cranked with having my foot held on the pedal, but as soon as I took my foot off the accelerator the car died, and I haven't been able to crank it since. I bought a scan tool, but it keeps saying its unable to connect to my car, but the scan tool works because I tried it on my other vehicle which is a 2005 Yukon almost identical to the 2004. At first I was thinking fuel pump, but with all of the electrical issues I'm having it's leading me to believe it's one of the computer modules. Abs and airbag light are still on, windows still wont go down, and I cant unlock or lock my car with the fob or the power controls on the door, and it still won't start. Plugs, wires, and coils are about 2-3 years old. Ive tried 2 different procedures for the ecm security relearn. I've unplugged and plugged all three modules back in. All of the wiring that I've looked at seems fine even the ones behind the engine block on the firewall. This is not a daily driver. I've put about 15000 miles on it in the last 2 years. Everything I'm reading online is making me think ecm or bcm. The security lock light on the instrument cluster is not showing up like with many that have problems with the ecm. Trying to avoid having to pay a fortune at the dealer, but there is a place online that programs new modules if you ship it to them along with the old one. What are your thoughts?
 
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