Thanks to all for the posts and information. The link to the thread from CEG on how the cats and sensors work was especially helpful.
I bought my car new, but the cats were replaced under warranty a few years ago. I can't recall if the O2 sensors were changed at the same time.
I just called my local dealer and they want $78 for one sensor. I never fail to be shocked at how much they charge for parts. The rep tried to make me feel better and make me feel like $78 is a bargain by saying he expected it to cost much more. Nice try.
Since my car isn't due for an emissions inspection for another 15 months, I'm going to go the MIL Eliminator route to solve my MIL problem.
Thanks for the help.
