service light on 04passat

i have a 2004 wolkswagen passat gls and i have recently installed a k&n air filter and ever since my service engine has been on i took it to a wolkswagen dealership twice and both times they reseted it and told me that theres nothing wrong with my car and it keeps goin back on. is there a way i can reset the service light myself, if so how?

No, the light must be cleared with a scanner. What was the code number? I've seen several contaminated MAF sensors from people applying too much oil to their K&N filters. If VW sees it they will void the warranty on the MAF.

whats an MAF also the mechanic that installed my K&N filter didnt add any oil to it he installed it as it came out of the box also my waranty with VW is void because i installed a dvd player and a boost controler if i take it to VW it cost money and light just comes back on anyways

Take it to an Autozone & have them tell you the actual code numbers they get. You need that info to diagnose it.