The US market was finally allowed to purchase a single choice diesel engine version of the ML vehicle in late 2006. Since day one of the release of this series car in the 90s it was available in the rest of the world with choices of two four cylinder diesels, two V6 diesel variations and now even a V8 diesel along with similar variations of gasoline engines - ironic since the only place they are made in the world is Huntsville, Alabama, USA. But I digress.
I ordered one in June or July 2006 with the factory installed trailer hitch and electrical package and it was in the first production run of October 2006. Then in December they made a small modification that impacts user friendliness installing a trailer brake controller.
The first three months they made this car, the interface plug from the car to the brake controller was conveniently located in the right rear corner of the car. Thus, one has to somehow sneak four wires plus a protective sleeve from that location, along the right side of the car and then across the engine/transmission area to the driver's footwell. Sounds like an interior removal and install just to get the wires in position.
In December of 2006, the factory installation option terminated that interface plug in the driver's footwell area.
And, by the way, the mating plug and four pins are conveniently priced at $34.20 plus local tax. If you have the wrong version of the "Rear SAM" module, that will be another significant expense.
(1) Molex connector housing PN# A039 545 35 28
(1) Pin 0.75 mm PN# A046 545 40 28
(3) Pin 2.50 mm PN# A035 545 74 28
If the "Rear SAM" is your vehicle has parts numbered A164 540 78 45 or A164 540 88 45, then the lucky customer gets to purchase:
(1) Rear SAM PN# A164 540 11 01
YMMV