In the drivers footwell under the dash, kind of over near the hood release. It's not a round one like the 38 pin, it's more like what the domectic manufacturers use, a 16 pin. It has a flip open lid over it. Most newer design MB's are like this, like the S, the new C, the new SL and E class, the ML's are all like this too, "it's just like the ML" (that would have been a shorter answer)

Gilly