Hey guys, ive been reading for quite some time now, and havent really been able to find any specific information on the subject, but also would like some guidance to help save some $$ :D So, i am pulling a CEL on my 09 Rx8 sport for my rear o2 sensor. I will be getting a BHR Midpipe here soon without a cat. So would it be a waste of money for me to pay (about $100-$130) for the Sensor just to replace the cat and sensor with an aftermarket midpipe soon after? or should i just use that sensor money towards my midpipe.

I definately appreciate everyones responce and contribuition to this forum i love it!

Rotor on.

EDIT: After further look into the whole midpipe and o2 sensor thing, that for proper installment, ill plug my o2 sensor into my midpipe, so there is no loop around. i have to replace my o2 sensor afterall. (i think)

 

What code are you getting? Have you tested the sensor itself to ensure that it is faulty and that the root of the issue isn't something else? Do you have to pass any type of emission testing?

Personally, I wouldn't bother if the sensor is in fact faulty and I have no plans to utilize any ECU flashing to mask a specific CEL (fortunately some options are slowly becoming available for the series 2). Once you install the midpipe, you will get a persistent P0420 with a properly functioning O2 sensor.

From what I've seen, the P0420 code only alters short term fuel trims by 2%, and at wide open throttle it has no effect.

 

Hmm, thank you for the reply. i have not tested the sensor by itself. i havent had the code tested in awhile, but i did get it tested twice and i searched all over the forums and came to the conclusion it was the rear o2, no i dont have to pass any emissions testing (at least not very soon at all) when i get the midpipe and install it i will check the codes again to see if its mulling more than just a P0420. Also good to know that it doesnt alter the fuel very much. I drove with the failed sensor for at least a few months, and there wasnt really any change in performce before or after i was pulling the CEL, other than a little less mpg.