Well, 1 step forward, 2 steps back. Got everything running, working through the usual, getting fluids warmed up and checking powersteering/hydroboost lines, making sure trans has fluid throughout the system and is working. Found that the CDL wasn't working and the 4WD indicator was staying on. So, a side quest...position sensors all bad, the CDL motor was oxy/hydrogen welded and no recovery from that. Got new sensors, and found a working CDL motor. All good now.
As I was doing checks on things and logging the engine, found that I was getting no readings from the MAF. While the engine/trans is a 2009, it must have been an early one as it has the 2008 tube/card hybrid MAF. Got a Delfi replacement easy enough. Once I figured out how to get the card out, sure enough the thermister for the IAT was burned out, made me feel good about just throwing the parts cannon at it and buying a new one. No joy. Then thought the cheap wiring harness may have had LS7 wiring to it, so swapped it. Again no joy. The original wiring showed a IAT of 67 (actual temp was ~63, close) but never moved. The rewired connector then showed 117, not close, and also never moved. Neither wiring showed frequency or any airflow. Found the connector on the original harness and the new harness was wired correctly, also checked it at the ECU.
In the process of gong through these checks while logging, I checked for DTCs, of course there were some (no O2s, the MAF, and AC pressures). I went ahead and cleared them, instant engine shutdown. Tried starting again, fires, then shuts right off. Tried multiple times with/without throttle, wait a few minutes, same results.
I've had this happen a few times now. First start did this and after a reflash of the ECU. At some point it would start again and be fine. Don't know if it's a wiring problem at this point or if it's a problem with the ECU or ?? Basically original stock tune, just a few things turned off (VATS, fuel pump set to static, starter diagnostics turned off). My fuel pressure gauge is wonky so getting a new one today so I can be sure the pressure is good. Doesn't seem fuel related, it doesn't starve for fuel, it just shuts off after firing.
Oh well, this is what makes these projects fun, right