Edmunds Answers



  • coldcranker 07/24/08 11:42 pm PST

    I had a similar problem on a vehicle just a while back, but the diagnostics were smart enough to actually tell me to replace the oxygen sensor downstream of the cat convertor. That being said, the error code you got could indeed be the downstream oxygen sensor acting up like you think. That is the oxygen sensor downstream of the catalytic convertor. One could pay about $70 to replace the downstream sensor (easy to do), and maybe the problem would go away without having to replace the cat convertor. Look at it this way: After 7 years, the oxygen sensors are about ready to go bad if they haven't done so already, so it really couldn't hurt to replace it anyway right now. A cat convertor is more expensive and might require a muffler shop to swap it out.

    There is a small chance a spark plug is fouling and causing this problem, so it couldn't hurt to make sure the spark plugs are in top shape, too, something a 7 year old car probably needs anyway.

  • peackpr9 07/27/08 7:29 pm PST

    Thanks Coldcranker. That's exactly what I was planning to do. My only problem now is determining which is which buying/replacing the sensors. I mean, are both the front and rear sensors upstream or downstream sensors? If not, which is up and which is down?


  • delliott2 04/06/10 1:53 pm PST

    I have a 2002 Mazda Protege 5 with the same error code. I had my oxygen sensor changed twice both back & front. My engine light has been on for two years. I had plugs, coils, fuel injectors cleaned...you name it I had it done and my light is still on.


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