@Dr Gil showed up with new OEM oxygen sensors he wanted to change out to start attacking a random P0401. I offered to just check the ohm value but he was sure that wanted the piece of mind of getting them replaced regardless due to age. He actually came by because he rounded out one of the nuts trying to get it off. Gave up before it became a problem.
I had plenty of tools to work around it so issues there. Tested the resistance value of both old and new sensors. All four sensors were 13ohms. Oh well, he's got spares now.
Then he wanted to get belt tension checked because his belt(s) have been squeaking. Using my new little Gates Krikit tension guide I got about 40# on the alt belts which were just at the low side. But then I checked the AC belt, it was like a trampoline. Totally loose. So loose it wouldn't register.
The problem here is whoever tightened the AC idler pulley decided to use the crank pulley bolt spec of 307# to torque down the idler lock nut. I didn't want to risk snapping it right before he was about to leave for a long off roading trip. So that belt will stay loose for now.