Engine light on, dont know why-2003 Jetta T1.8
 

I just bought a 2003 Jetta T1.8 and after driving for a while today I started the car back up and the engine light / image lit up and stays that way. The car is driving fine, not overheating and I"m not aware of any other change in performance. Any ideas why this could be on? I don't have an owners manual to check it out-