I had my 99 golf gti at the dealership today and the lady there was saying something about aftermarket sterios use the port they plug into or somthing to run the diognostic on the car. This concerns me because i am something of an audiophile and am planing a total reconfiguration of the audio system starting with the head unit. She said that would be fine so long as i kept my stock two din radio. She also said my new one would have to come out if they needed to run a diognostic. Does anyone know about this or if there is a way around it or what? Any help would be appreciated thanx.

 

I'm not 100% sure it applies to the 99 but on the newer models the radio has the ability to be checked by a scanner for problems. From what I heard the aftermarket harness that plugs into the VW wireing has been known to short out the diagnostic tool.

 

if you get a harness made for a vw install it all works fine.
you need to follow the instructions that come with it