2002 5.4 xlt

I'm using the Torque App to monitor my engine.

Noticed both o2 banks upstream sensors are always a up and down .1 to .7 at idle. Both banks downstream sensors after the cats pretty much sit at .7 the entire time at idle.

Are the downstream sensors supposed to be changing up and down like the upstreams do?

 

THink I finally found my answer... read where if the Cat is working correctly, the downstream should stay at .45 or higher and be fairly steady.

 

Yeah all the downstream O2 sensors do is monitor cat efficiency. Your exhaust gases after going thru the cats should be consistent, so in this case, the less change you get, the better.