Frank I understand what James is saying, yes it would be nice to place a message on the CAN bus telling the CCU or node to carry out a particular command, say unlock the N/S/F door and seeing this operation take place, also to then Scan the bus for the message being sent to the CCU or node, in this way we could eliminate each node and the CCU from being faulty, instead of doing like a lot of dealers do at the moment just replacing the part they suspect and then move onto the next and so on, which is impossible to do if you are repairing a number of different manufacturers vehicles, besides this being the wrong way to go about repairing these systems and unfair on the customer,
we might then need a database of messages for each manufacturer or maybe each model of car on the road with CAN, with a command list we can understand relating to each message, this would be some database, now is this the way you are looking at testing CAN if so I am very interested.

Regards
Tom