When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
When the forward (pre-cat) sensor is not functioning, the PCM will go into open loop, which basically means it's going to get the A/F mix from a pre-set parameter table programmed into the PCM. This usually will mean a richer mix than when in closed loop as the PCM "thinks" the vehicle is warming up.
Okay...so I'm guessing the PCM is misinterpreting something then? Now I'm not the original owner, but what if the previous owner used some kind of superchips to tell the computer to run in an economy mode. I'm assuming that adjusts the A/F? Just a thought..(since I can't explain this phenomenon)...what if the computer has those settings configured, and the O2 circuit overrode those settings? I don't know how those programmers work on a long-term basis, so I'm just curious.
Heck, if I'm getting better MPG, screw these things...I'll just get a simulator to eliminate the CEL.
