16197427, $OE, AMC 401, Oxygen sensor goes super rich does not move

[babywag]

is this a new sensor or used?
they do go bad sometimes.

[rang-a-stang]

Brand new to this install. Efi side connector from a wrecking yard, though. Maybe I’ll go 3 wire? That should be an easy swap from where I am right now.... hmmmm...

[rang-a-stang]

OK, progress.

First I ran a dedicated ground from my ground bolt to the O2 sensor ground. Fired it up and I went to closed loop idle pretty quick. When it was cold, it idled amazing. Then, all the sudden the O2 sensor started swinging from 50mv to 1100mv, wildly/quickly. So I shut it down and connected A12 to a direct/dedicated ground just like the oxygen sensor output. Same result (swinging O2 sensor). I didn't have time to tinker much more and did not take it for a ride. If I rev it, seems to have good throttle response but also has a bit of a backfire in there.

What should I do next?

[rang-a-stang]

Ok, all done! Had a bad rotor in the mix. O2 sensor works great now, and the truck runs well! On to tuning! Thanks everyone!