Originally Posted by
centerforce99
You would also have a CEL if the 02 sensors were bad. These don't get lazy, they work or they don't.
I have always heard that an O2 sensor can fail, but will not always trip the CEL. From what I recall, if a failure occurs they are designed to make the engine run slightly richer instead of lean to protect the engine. A sudden drop in gas mileage is an indicator of this condition.
Has anyone else heard of this condition?