ITRCA

My car is throwing the ol' engine code 1 at me. Something is wrong with my O2 sensor... again. I just replaced little more than a year ago too. I'm looking at buying a new one and installing it.

I'm thinking Denso or an NGK, but I noticed there were part listings for a front and a rear.

What does this mean? Are there two O2 sensors or just one? I looked in my tech manual and it only shows one sensor just in front of the cat behind the header. I'm confused about the right part #. Can anyone straighten this out for me? Thanks.

there are in fact 2 sensors. The primary as you described and a secondary that's downstream of the catalyst.

there's no need to do anything with the secondary sensor, it will only throw a code when either the sensor fails, or the catalyst becomes inefficient.

I found the two sensors to be interchangeable.

Thanks. I think the second one might be bad. I'll need to check it out.