Check Engine Light??? What are the diagnosis?

Hello all,
 
This is part 2 for my recent symptoms to my 2000 Golf. 
 
As mentioned in my prior posting I had water coming out of my exhaust after a 15 degree day we had in NY and upon driving my car for a few minutes the check engine light came on. 
 
What are the usual diagnosis for a check engine light? 
If it's not anything serious does anyone know how to turn off the Check engine light sensor for a:
 
VW 2000 Golf GL? And will a special tool be needed or not?
 
Thanks and I welcome any feedbacks.