Lamda sensor

[AdvocatusD]

I think I've got a lazy Lamda sensor (hope that the right spelling!), which explains the crappy MPG (14 MPG!) the car's been returning me over the last month. If it is the sensor that is awry, how much should it cost to put right? Also is this a job I could take on myself at all? I suspect not, given it probably needs to be set after installing?

Other than the sensor, I am happy to report that the car has been just flawless!