My check engine light came on, so I brought the ol' girl down to AutoZone, and had them read the code, P0136. So a new oxygen sensor is around $55, and I don't feel like spending that until I have to get an inspection come January. So my question is, will not having a functioning down-stream 02 sensor cause any problems? And I don't really care about pollution... haha

 

well..if your talking about the O2 sensor located after the cat...it's only purpose is making sure the cat is working properly. If you have a faulty cat then you will get a (cel). If you have a faulty cat, you might get poor performance because the cat is clogged or starting to break up and of course bad emissions.

If you have a bad O2 sensor after the cat...you will get a (cel) but it wont affect performance or emission.