I own a 2003 MCS with 78000 miles and for over a month now I've been dealing with my check engine soon light tripping because of the rear O2 sensor. For some reason I'm running lean and the only improvments I've done is add a CAI. I took my mini to the dealership last week and they suggested for them to reprogram and if the light came on again then we would replace the O2 sensor. Well needless to say the check engine soon light came on not even a week later and now they want to bring my cooper back in so I can spend another $350.

Can anyone tell me if changing the O2 sensor is easy and maybe recommend the best replacement O2 sensor for the money. I also need to know if there is anything else I would need to do after the install and do I need to find a way to reset the engine light or will it just go out on it's own after the new sensor is installed? I've had this cooper in the shop alot in the past 2 months for some reason and with the holidays my money is a little short right now. Thanks again for everyone's time and advice!

 

What is the check engine code?
Is it really the code for 02 sensor?
When the engine throw a code there should be an associated fault code.
Why guess?

 

Also check that your car was not included in the o2 sensor warrenty extsion to 10 yrs/100,000 miles. A wick search on here will get you the copy of the letter.

 

Thanks for the info! I tried to search it out but came up with 0 results. I'll keep looking!

 

Autozone has bosch 02 sensors for $180 and helix has them for $215, so you could save a little money through that.

 

Just checked with the dealership.. My vehicle doesn't qualify for that warrenty extension. Thanks for the info though! Back to the drawing board.

 

I had same issue with my 03 MCS DSMINI1. First of all there are two 02 sensors on our Mini. One before and one after the cat. The one after the cat merely measures the "health" of the cat, that is all. The pre-cat O2 sensor actually helps to make your MINI run properly.

I run a CAI and eventually started logging "lean on bank #2 codes". It is not good for the engines to run lean. I added a set of JCW 380 injectors and the lean codes went away. As did my cold start issues, ( Mini Flu ) and runs like a top.

By the way. I also replaced my pre cat 02 sensor....and wasted about 200 dollars. the old one was clean as a whistle.

Good luck.

 

First things first: pull the code. If you don't have a OBD reader, try Autozone: they do free scans and will tell you what your fault code is. Post it, and go from there.

 

You can also try swapping the two O2 sensors to see if anything changes. They are identical.

Ken

 

What is the code?

You mentioned lean running and a rear O2 code? while these two are not mutually exclusive, it is possible that a lean running engine will produce feed gasses that are outside the catalyst window thereby forcing the rear sensor to stay low when it should be above .45 at idle if the engine is warm.

Be advised that if this is the case then the front O2 sensor may not be reading the exhaust correctly resulting in the ECM commanding a lean condition....at this point every thing is happy!....however since the rear sensor is the only that has not lost it's mind it is saying "I don't care what anybody thinks! this pup is running lean!

If the front O2 is commanding a strong lean correction the fuel trims will be on the high side. Also check MODE$06 (results of the non-continuous monitors) to see what the response time is for the front O2.

A slow responding font O2 will manifest itself through a short term fuel trim that exceeds 8%. Thees parameters can be observed using a compatible OBD-II scan tool.

Good Luck