check engine light-all wheel drive button

I have a 2001 S40 Turbo with 110000 miles. Last winter my all wheel drive button got stuck, I was able to clean around it and get the button to move freely again. When getting stuck the check engine light came on and since getting it checked by a few mechanics, a transmission code that they can not reset is causing the check engine light to stay on. I have had my transmission checked a few times and am told that the transmission is fine. Now I have to get my car inspected and have no choice but to go to a volvo dealer...anyone have any advice on transmission codes? I am trying to avoid paying for an unnecessary hook up to their diagnostic system ($250) then them taking my console apart $(125). Well, I just found this site and am dropping my car off this morning, I will let you know what happens and you can tell me if I get ripped off AGAIN