I have added a Kenwood video head unit with navigation to my 2000 E430. I have taken it to several radio installation shops and no one can locate the VSS wire for the navigation system. They are telling me that I need a canbus adapter to convert the signal from digital to analog. Can anyone tell me where the VSS wire is located and if a canbus adapter is the solution. This adapter is $200 and I don't want to spend that if I don't have to.