Question about O2 sensors on chevy tbi

[MxRace75]

Just put a new O2 sensor in a 95 Suburban and pulled some data from it and it swings from 800ish mv down to 50mv and back to 800.. Is this normal??

Attached pic is about a minute of steady state driving - no fuel enrichment - no egr

[RobertISaar]

during closed loop operation, that is entirely normal.

[MxRace75]

I was just surprised to see such a big swing. I would have thought it would be a couple hundred mv not 700

Thanks

[RobertISaar]

that's just how narrowband O2 sensors work. if there isn't a very large swing, the sensor is getting lazy, or it's cold or the control scheme is SUPER tight and not swinging the AFR around stoich nearly as much as other systems.