i wonder if anyone can help me with a problem i am having with my rs octavia .despite having returned the car to the main dealers the engine managment light continues to stay on i have been told that this is a lan sensor problem any know what causes this thanking you

Do you mean 'lamda'?

Any idea what the fault code is?

Could well be a air mass meter fault (MAF) ive seen a few of these recently bring up a lean mixture fault which brings the light on. Lambda probes are also quite prone to go.

thank you ross .what effect wiil this have on cars performane and how expensive to rectify

Is your car still under warranty,did your dealer say he would fix it,who is your dealer? BTW Pinocio welcome to the site