Looks like vehicles with rpo Z75 - E52 have that circuit board. .. but anyway since you said you disconnected the connector and reconnected disconnect that same connector and with a pair of needled nose pliers slightly twist the male terminal connectors so that it assures a good connection also see if you can trace the black wire to it's ground location and make sure thatsnice and tight if none of that works you may need to replace the tail lamp harness assy for that side unfortunately I think you may have to purchase the hole tail lamp assy from the dealer so you may need to see if one is available online