Quite a lot of people on here have VCDS which can scan for errors. My light came on and with the help of SqueegeUK were fixing the issues that were thrown up. As I drive a 1.9TDi, the first thing was the glow plugs as 1&2 were intermittent, and the next thing we are going to change is the fuel temp sensor. Which was the only other error.
Basically many people have had the same problem and it can be thrown up by many different things. So the only decent option is to get your car scanned. There is a thread on here giving who had the equipment and where! Hope this helps!