I finally had a chance to check the black box. Pins looked squeaky clean but used contact cleaner on them anyway. Opened the box like you did; everything looked perfect. Checked continuity between pins and board traces; all good. Put it all back together and turned the key but no change, so the contacts don’t seem to be the problem. I probably need a decent scanner designed for the car. Any suggestions? From my own research the iCarsoft MBII, iCarsoft MBb v2.0 and Foxwell NT510 Elite Scanner for Mercedes seem to be highly rated. The Foxwell may even be programmable for other vehicles; I am checking on that.