EML - code P114b - o2 sensor

[Z4_ATB]

The EML has come on twice now with code P114b being stored - I’ve done a search and there seems to be so many recommended solutions from changing fuel (I’ve recently switched from BP 97RON to Tesco 99RON) to it being an o2 sensor (1 of 4?) to an air leak to MAF sensor needing a clean etc - any recommended starting point?

If I erase the code it seems fine for a few days

 

[Jfgoldfish]

It's most likely not the fuel unless the stuff in the tank is very stale and nasty. No need to run these engines on higher octane fuel.

What do your fuel trims look like? Long term trims should hover around 0 between +-5ish.
The MAF sensor is also an easy start, check it responds to throttle input, and that it's reading is plausible at idle.

I highly recommend getting set up with a K/DCAN cable if you have not got one. That will allow you to perform far more in depth diagnostics and potentially save a fortune.

 

[colb]

Check all rubber inlet and vaccum hoses and pipes for splits or holes, unmetered air that is getting in after the Maf sensor will be picked up by the exhaust sensors and lead it to believe the engine is running lean. In order to compensate for the lean condition it will add more fuel at the injectors to richen the mixture up. It will continue to do this until it adds up to 20% more fuel, if it still fails to correct it will set the EML and codes. If you can't find any holes or splits a smoke test would probably find any splits or holes.

 

[ph001]

Vacuum leaks are not very common on the N52 and MAF problems can typically be identified by the idle revs rising when you press the brake. They also don't suffer the same emission related problems that plague the 2.0l so I wouldn't suspect fuel either.

I would have the o2 sensor at the top of my list.