Hey, man.. Jim just did a VERY thorough explanation.. read up on what he just wrote out.
Upstreams are the ONLY sensors that determine a:f ratios.. downstreams determine catalyst efficiency.
If you think that your code IS from a faulty sensor (and not that your car is actually lean) then it would be the UPSTREAM sensor, on that bank.
A downstream fault would trigger a catalyst below efficiency code.
Ray
Last edited by Ray; 06/07/05 08:35 PM.
