2004 Chevy Trailblazer EXT LT 5.3L V8

2004 Chevrolet Trailblazer EXT Description

I have a 2004 Trailblazer EXT LT 4X4. Towing package, Auto transmission, 5.3L v8, lots of power, interior & exterior in good shape. power everything, moon roof, both front seats electric and heated (w/ memory seat), 3rd row seating, integrated garage door buttons & voice memo recorder...
New: 4x coil packs, spark plugs, wires, Downstream o2 sensor, fuel pump, fuel filter, air filter, MAF sensor, MAP sensor, both Catalytic converters, Both Upstream O2 sensors, Intake Manifold gasket. 4 BRAND NEW TIRES.
The bad:
I bought this car off of a guy up in Marion Heights, PA, who swore up and down it was a 'good car'
I have had an engine light on since I bought it, and have had no luck diagnosing the issue (as you can see with all of the parts I've stuck into it) It's so close to running great, I just have no more money left to put into it. I've dropped over $2000 dollars on parts into it, in the last 3 months, and have it narrowed down to bad O2 sensor wiring or a bad ECM. If someone took and put the time into it, they would have a great running vehicle with a ton of new parts. I just want the 4500 out of it, that I initially bought it for. There's a lot more money invested here... and I am just flat broke, and unable to keep working it out.
Has a tiny bit of surface rust on bottom corners of back hatch.. aside from that, completely rust free.
asking $4500 for a very attractive vehicle, that just needs a problem sorted out.
Mileage is 153000, but rises, as it's my daily driver.