How about to simplify, I'll plug back in the relay for the cool fan. Then drive it till it throws a CEL again.

The crankshaft relearn is a must right? It's not like the new ecm/ecu learned it without a tech2 put to it, right?

 

Right, unless it was deleted.

 

I did disconnect the battery a few times after replacing the ecm/ecu. Codes have been deleted that way. So, gotta do that crankshaft relearn anyway, right? For doing crankshaft relearn:

• I called one shop and the fella said $250, because they're gonna call in a tech service to come out to their shop and do it.
• How much would dealership charge? Seems like it should be closer to $75.
• I just moved and our good family mechanic's shop burnt down, he's done/retired and gone back to farming and being retired. So how to find a good mechanic with tech2? Just call around?

 

GM usually charges 1 hour labor. Your telephone will help you more than someone in Virginia.

 

Alright, so... fan still runs continuously, no ac, no ac clutch engaging.

• Replaced the dexcool, thermostat(131-158), and ect sensor.
• (Also, maybe unrelated, got the crankshaft relearned at dealer to follow-up ECM replacement after P0606 (internal fault in ECM))

 

You already replaced the BCM and ECT, that narrows it down to:
* stuck relay?
* somebody thought they were smarter than the designer?
* maybe the wire to the ECM is shorted.
not much else.