[GCusson91]

So I have a 2010 328i LCI with M-Sport package but I believe it has an N51 engine (not sure if that relevant or not).

So basically my SES came on about 3 weeks ago when I started my car the first time after a 2-hour drive. At first it was intermittent but after about 250 more miles it came on and hasn't turned off by itself since.

I initially got the code read at auto zone but they just have a generic reader and it read error code 2096 Post Catalyst Fuel Trim System Too Lean Bank 1. They didn't reset it at that time but I read about BMW codes so i bought a cheap BMW code reader just so that I could scan and reset the codes myself.

The scanner I have does a DME scan and it keeps returning the code 2c31 Lambda probe in front of catalytic converter, trimming control. Seems to be opposite of what the auto zone scanner said but given that its a bmw code I think this may be more accurate.

I have reset the SES light by erasing the 2c31 error code. It will stay off for a while even if I restart the car multiple times but usually anywhere between 5-45 miles (generally 24-48 hours) it will come back on. It always comes on while I'm driving not when i start the car in the morning or anything. It also seems to be more common to come on, on the highway rather than on city streets.

I am considering replacing the 02 sensor but I want to verify that that code is related to the Pre-Cat Bank 1 Sensor. Also it seems like another potential reason for the car to throw that code could be an exhaust leak. Is there a way to check for that without special tools or a vast knowledge of exhaust leaks?

Overall the car runs fine there is sometimes a rough idle for a second at like a red light on my first drive of the day but it goes away quickly and never comes back even at the next light. The gas mileage seems to be the same as it was before and I just don't notice any major changes or problems.

I would love to get this fixed so I don't have to erase the code twice or more a week but I don't want to replace a bunch of parts that aren't causing the problem or pay a shop to diagnose it to tell me its just the 02 sensor. So, I am reaching out to you guys to ask if you have had any experience with this issue and potentially would have any recommendations on how to fix it.

If there is any additional information I can provide please let me know

Thanks a lot.