My '08 base model (72,000 miles) gave me at the check engine light a couple of months ago, so I pulled the code to see what repairs it might need and it ask me for a new thermostat housing, so I replaced it.
A couple of hours later the dreaded check engine light came back, but this time it gave me a p0136 fault code which pertains to an O2 sensor circuit (bank1 sensor 2). So I replaced the second, after the CAT, with a NTK sensor. Cleared the code, drove it for about 3-5 mile and the check engine light came back!!
So I checked the codes again and it gave me p0136 again!
Was i supposed to change both sensors?
Does my CAT needs to be replaced?
Any ideas or suggestions will be greatly appreciated.

 

Any ideas?
Anybody?

 

Stock exhaust? Might want to check the condition of the cat.

-Luccia

 

Yes, everything is stock.
How do I check the cat?

 

Just to clarify one thing that I might have done wrong.
The sensor that I replaced was the one that BEFORE the manifold, after the cat; not the one between the engine and the cat. Was I supposed to replace the one that goes between the engine and the catalytic converter?

 

It is for the post cat sensor. I'm pretty sure that DME is covered under a special emission warranty for O2 sensor issues. Make sure the valve cover gasket isn't leaking into the wiring harness or the O2 sensor. If the V/C is not leaking now, but was in the past, check to make sure there is no oil residue. If all is well there, check with your dealer about the warranty as it's, I believe, 10 year or 100,000 mile warranty on this particular issue.

-Luccia

 

Do you have a link to an info sheet regarding the warranty?

 

I don't think it is covered. http://www.epa.gov/obd/pubs/420f09048.pdf

 

Unfortunately not. A Mini specialist here advised me about it and said the best way to find out if someone qualifies is to call their local dealer.

-Luccia

 

Good luck with contacting Mini dealer. They want to hit you up for a diagnostic fee before doing the work or telling you if it would be covered.

 

That's opening a can of worms.

 

I may have to do that. One of the reasons that I needed to fix the check engine light was because I have to do the smog check and it failed for the reason previously specified.

 

Is the NTK the OEM sensor? I've heard reports that some sensors don't play well. Not sure if that is the case here.