I got mine done at the dealer as car was still under warranty, apparently they'd never seen a car with the problem, then when I went back a year later with the same problem the comment went along the lines of "we did one of these a year ago, don't get them very often..." Not a massive amount of help to you, sorry, but part of my problem may have been a bent prong in the connector, they are a bit fragile. Think it had been bent when I had the downpipe fitted and they plugged it back together as cel came on instantly, "that'll be the lambda sensor sir" followed by mass panic when it wasn't lol!!! It was recommended to me on here that you remove them but I chose not to, didn't look to be that much cheaper and then the possibility of other stuff to go with it i didn't bother. I can see why they're there but a bit of a PITA IMHO!