Thanks Warren,

...but everything I have seen on the Braingears site is right out of the MB Service Manuals. I have the all the paper manuals for my car as well as applicable software.

My original question regarding the location of the N3 control unit is because all of the wiring diagrams I have seen, and the comments posted on this forum are regarding the a 25-pin N3 unit. My unit is a 52-pin and it was causing me a fair amount of confusion since I was trying to trace my O2 signal wire. I was looking for a wiring diagram that displayed the 52-pin unit.

The EPC shows a part #011 545 28 32 for the "MSG Control Unit." The MB part # on the unit in my California car is 011 545 01 32. It has three rows of pins (18,17,17). It is making it a pain in the ass to troubleshoot the CE light when I don't have an accurate wiring diagram.