Quote:
Originally Posted by slodave
I'm going through this with my Corolla. The secondary O2 sensor apparently does what you said. Sigh, I am going to replace the sensor first. A cat is over $1200.-.
The sensor is supposed to trip the CEL at about 50% efficiency.
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ahem..a word from someone who sells cats for a living...your corolla has a program flash at the dealer to "eliminate" the rear o2 senser..and fix persistent
p0420 codes
second the role of the pre cat o2 senser is the same as it always was..it is the mixture regulation control...the after cat sensers are "nanny" devices that ONLY moniter catalyst efficency...they play no role in mixture unless you have a VERY late model car(even then it is really only long term fuel trim)