It might be standard issue, but it sure as hell isn't standardised. For instance: some (all? It's been a while) BMWs have the engine's CAN bus available on a

It might be standard issue, but it sure as hell isn't standardised. For instance: some (all? It's been a while) BMWs have the engine's CAN bus available on a couple of pins in the OBD-II socket. If you knew what you were doing, you could have an awful lot of fun with that, but the chances of it being compatible with any other manufacturer out of the box? Slim. And it certainly isn't read-only :-)