Got another one here.

On a Ford vehicle that uses the SCP bus, if a new module is connected to the bus (ie, a installing a factory option that uses a module, but the option/module were not original to that vehicle), will the module simply grab and use whatever data it needs from the bus or must something be programmed to acknowledge the existence of that new module?

Said another way, is the data on the SCP bus up for grabs by any module simply wired to it and the module is able to and is designed to communicate with the SCP bus?

On the "BUS", modules "talk" to each other. So, it is "pre-ordained" as to what is included in the vehicle. You do a network test with the IDS and it will display what is included in the vehicle. Run the VIN on "DOES" and it will show all options from the factory. Extensive programming would be necessary just to add another module (not really sure if it would even be possible). Making sure that it was added to the correct network (HS can-MS can) would be headache enough.

Thanks Vince, the answer is appreciated. What got me thinking about all this was, I confirmed yesterday that vehicle speed and engine temp data for my vehicle are in fact on the SCP bus, and with this in mind the hope was that an EATC head unit that came from a vehicle (Expedition) that used the SCP bus to feed this data to it could simply be wired connected to those two wires for the SCP bus in my vehicle, and it wold be up and running. The "little surprise" that cam about was during testing, when it was noted that the unit was quick to respond to temp drops, but TERRIBLE at responding to temp increases (Expy head unit displays outside temp). Hence the communication question.

Time to ponder options, thanks again!