My '16 base model has the check engine light g=coming on and off. the code is P2096 post catalyst fuel trim system too lean and P2396 O2 sensor signal biased/stuck rich. I suspect this is all about the Cat convertor. Is this serious needing immediate attention?
Thanks,
FredV

 

If you can get the BMW / Mini DTC code instead of the generic P-code, you can further determine the cause using this site:
https://bmwfault.codes/

I would be tempted to lean on the primary O2 sensor as needing replacement.

 

Troubleshoot and fix the O2 sensor code before considering a Cat issue. And as mentioned above, BMW fault codes yield more detailed information.

 

That would be my guess as well. The primary sensor is stuck full rich so the ECU is leaning out the mixture as much as it can, and the post-cat sensor is correctly showing that it's lean now. Yes, this needs immediate attention, as driving with an incorrect mixture can damage your engine or cat converter.

If your primary sensor has more than 60K miles on it I would probably just start by replacing it. They do wear out or fail and 60-100K is probably full life in most cases, so that wouldn't be wasted money.

Also note that this is the R56 2nd gen forum, if you have a 2016 you have a 3rd gen and are in the wrong forum.

 

Another caveat is that BMW Fault Code Lookup does not find fault code P2396, so it's unclear whether or not this code indicates "O2 sensor signal biased/stuck rich".

If the 2016 Mini Cooper has DME variant MEVD172X, then the service plan for code P2096 is shown below. As a first step, you may want to consider looking for an exhaust leak before the primary O2 sensor and an issue with the PCV system.