Mike,
I cannot say if the J1939 Bridge was used prior to 2006 model year, it would be interesting to know for sure, but I have found little information relating to the module. I found the Bridge Module on our coach while troubleshooting an issue with the Check Engine and Engine Warning lamps. I had a Cat technician tell me that the Check Engine, Engine Warning lamps and dash gauges were controlled by the Aladdin system and that the Aladdin system was the cause of our lamp issue (he also noted the inaccuracy of the engine and trans temp gauges). I did not buy his explanation, so I started researching.
I obtained a diagram of the J1939 backbone from REV in Coburg. That diagram showed various branches and terminations including the front and rear diagnostic ports, VIM connection and the Aladdin connection. It showed the Aladdin connection to be forward of midship. That is how I found the Bridge Module; I did not know it existed prior. When I found a module that was labeled J1939 Bridge I thought, oh boy, the technician was right after all.
I spent several more hours reviewing diagrams and troubleshooting our Aladdin system, what I discovered is described above. Also, disconnecting the Aladdin VCM Engine Bus or the J1939 Bridge (one at a time) had absolutely NO effect on the Check Trans Lamp, Check Engine Lamp, Engine Warning Lamp, or dash gauges. All that did was to cause the Aladdin system to display all ‘Xs’ for the engine and trip information and the system would not power on or off with the ignition switch. Same results when pulling the fuse in the Front Run Box. As I suspected, the ‘dash engine information’ on our coach is analog and not at all controlled by the Aladdin system.
I do not believe that the multiplex system plays any part, the multiplex system is for the domestic side of the coach, we do not have the Kongsberg chassis mux like the later 2008 and up coaches do.
In terms of the pin marked ‘fuel sender’, I did not trace that circuit, I suspect that it is not used in our application.
The diagram that you included is also in the Aladdin troubleshooting manual, it is not correct for our coach, it may be for an older versions of the VCM. That manual is helpful but seems to contain several errors and leaves a lot to guess work.
I have misplaced the diagram of the J1939 backbone, if I find it, I will post it to the group.
I used the diagram below and the detailed diagrams of the Front and Rear Run Boxes to determine the circuits powering the Aladdin VCM.