I have a 2004 manual RX8 with around 70k miles on it now.

The car started showing a CEL a few days ago and my mechanic pulled the code and told me it is the oxygen sensor in bank 1 sensor 2.

Is that the rear sensor? If so, would that be OEM part N3H318861B9U?
I can get the OEM sensor for about $120. I have seen after market by Bosch go for around $90. Is it better to pay the extra $30 and get the OEM? If I need the rear sensor I know that they are not as important as the front ones.

Is this something that I should event attempt replacing by myself? I do not have a lift so the best I could do would be to use jacks to raise the car.

Besides the CEL the car seems to run fine.

Thank you for your advice.

 

Yes, that would be a CEL for the rear sensor. The sensor itself is just a data sensor, telling the ECU if the cat is working fine or not.

So the question is, WHICH CEL did you get? Some of them indicate a failing sensor, others indicate a failing cat. Replacing the sensor when it's the cat that's failing is a waste of money. Ignoring the cat if it's failing is dangerous to various car parts and possibly the occupants (if it gets far enough to start a fire)

If it's actually just the sensor itself failing, then you can safely ignore it, but you won't pass emissions tests (that look for emission related CELs)

Removing it is fairly simple, in theory, but they are often rusted/seized in there, so it's a toss up on if you can get it out yourself.

 

I removed the rear oxygen sensor last week on my '05 RX, in fact (I'm an auto tech student, and we were assigned a back pressure test on a recent project). I was fortunate enough to have a lift to use. You should be able to do it with a jack/stands if you don't mind crawling under. Though you might have a clearance/leverage issue if you need to use a power bar to twist it off.

To remove the sensor you'll want (Besides basic tools) an oxygen sensor socket bit (It's a deep 7/8" with a side gap, so you can get it around the wire), or an oxygen sensor wrench. I had only a bit of trouble getting mine off with an oxygen sensor wrench, with no rust at all. If you have rust, you might want to try using some liquid wrench and/or a power bar.

My CEL came on afterwards, and cleared itself the same day. If you have access to a code reader, you can clear it right away.

Do you know exactly what CE code was generated?

 

Thank you for the replies and information.

Unfortunately I do not know the exact code the mechanic pulled. He just told me that it was the oxygen sensor in that bank. He is a good mechanic so I would assume he knows what he is talking about.

I think I will order the sensor online and have the mechanic install it. It is getting too cold to be outside messing under the car.

I have been driving with the CEL on and the car is driving fine, so I am in no hurry now to spend the money to fix it. The gas mileage seems as bad as ever, so no change there.

Thanks