Can anyone tell me if there is a relationship between the O2 Sensor and a vacuum leak? I brought my MINI in for a 02 sensor replacement and not 2 days later the check engine light came back on...it's in the shop again and they are looking for a vacuum leak.

 

Vaccuum leak lets unmetered air into the engine. The 02 sensor is what the engine uses to pick that up.

 

Yeah there is a relationship between the 2... if its for the same repair and same codes the old 02 sensor may not be the problem

 

+1 to possible vacuum leak. Also check for exhaust leaks.