O2 Sensors - Upstream vs. Downstream Function?

[BTR]

2000 Explorer XLT 4DR 2WD. 4.0L SOHC JOB 1 (VIN E). 5-Speed Automatic O/D 5R55E. 158,000 miles.

I know the upstream O2 sensors (1-1 and 2-1) tell the computer to adjust fuel flow to each bank. However, I'm curious about the downstream O2 sensors (1-2 and 2-2). I know they monitor the cats, but do they also tell the computer to adjust fuel flow? Or do they only monitor the cats?

Thanks.

 

[410Fortune]

They are only catalyst monitors

The upstream sensors are used by pcm

The downstream simply monitor efficiency of the cats

You got it! Confirmed