Is this OBD2 a single channel device, or does it support multiplex functions?
So on post 2001 machines, you can access lots of different controllers?
I am not certain, if you mean that can it handle monitoring multiple setting thean yes it can. It has a huge list that can be monitored.
Sorry, might not have been clear.
There are lots of controllers in the system (that's part of the problem people have diagnosing problems) and so you need to interrogate each of them to find the fault codes.
However, the big hitter is the engine ECU, and I understand that is the default connection. (Each controller may have many parameters that it can transmit, so even the engine ECU can be impressive)
But, being a CAN bus car, you may be able to get to other controllers.
For example, when I had my car checked at the local indy, I got the report from the CCM (Multifunction control module) that it could not talk to the A37 PSE (which is not a surprise, since it's missing, but is a diagnostic function I had not expected to be able to find)
For the 38pin connector, the diffferent controllers use different pins; I'm not sure how this is done for the 16pin OBD2 connector, unless the bus is multiplexed.
Hence the question.