Hello. New owner of a 2009 Clubman model (showroom clean condition). Check engine light accompanied by "increased emission" warning. Does anyone have an inexpensive alternative to the $250 Denso sensor? Also what size is the nut on the sensor? Any tips would be appreciated. Thanks.

 

There is an upstream and a downstream sensor. I just ordered the downstream sensor (after the cat) for my 2009 Cooper S from Aliexpress for $14.39 USD shipped. I found it by searching the Bosch part number. It's a bit of a gamble, but I've had good luck buying parts from there in the past. However, if you want to be certain you're getting the correct part with good customer service, I'd check the ECS Tuning website. They had an NTK sensor for my car for around $77.