wow.. that's vague... it just came on? nothing changed, you didnt do anything etc?
if that's the case you're only option is to find a dealer or independant garage with hy-scan to read the fault code.. it shouldn't cost too much to get it read then you at least have something to go by
:lol: can you give us abit more information mate? Is the car driving any differently? sluggish, juddering etc! is it on permanently or just after a while? :lol: you get the idea! The more we know the more we can help!