I needed to SMOG my RoadTrek - Mercedes Sprinter Van to renew the registration, but when I picked it up from RV storage, the check engine light was ON. I took it to Walt's Danville Service, because Wally had helped me in the past with a vehicle that was causing me problems. The codes were not clearly showing what the problem might be, but Wally and his crew took a methodical approach and just plain didn't give up. They contacted Mercedes for their help and eventually solved the mysterious computer problem and it passed SMOG! I am forever grateful for their commitment to get the job done, for keeping me informed every step of the way and for not charging me an arm and a leg for their many hours of labor. I will be back with all my other auto mechanic needs. THANK YOU!