No codes and we checked all the obvious things. When I asked this question I had a clue but wanted some confirmation. I spent much of the day on Mitchell-on-demand and AllData. Here's what I figured out (but won't be able to confirm until tomorrow). It is a combo MAF/IAT with 5 wires. One 12V and an input wire for the ECM (IAT), and three for the MAF, a ground, a 5V, and another input for the ECM. We had no 5V signal, in fact that wire was grounded. Until we unplugged the ECM. When we tried manually applying 5V, we popped the 15A ECM fuse (didn't see that at first). So, tomorrow we cut the "gray" 5V signal wire at the ECM, apply 5V from one of the other lines (such as the MAP) and see what happens. We might be able to cheat the system, but my diagnosis is a bad ECM!
I asked this question on justanswer. Com a few days ago and they were all clueless until today when I hinted at the answer. I wish someone would have steered me in the direction on how to check a MAF in the first place!
Friday, March 19th, 2021 AT 9:48 AM