I didn't find any DTB's but I found some information in my T.A.C notes that may help. The area behind the rear seat is where the speed sensor wires pass from the outside to the interior. The grommets can fill with water and corrode the wires to the point where they can break. I don't have an ML in the shop with the interior out at present, and I don't remember exactly where the wiring passes through, but I would suggest having a look beneath the carpet and inspect the connectors closely. I've never actually seen this happen on an ML but as I said in an earlier post, I see lots of 220's with this problem.

We have had dozens of those (NE Ohio loves salt!!), and that whole harness was replaced anyway.
Taking Steve's suggestion today, I switched the LR and RR pins at the controller and the problem didn't move, so we have a control unit coming tomorrow for it- I will let you guys know what happens!!