Indeed, some folks will reverse engineer it.
really interesting read...Exclusive: Say Goodbye to Chip Tuning – Open CAN Bus Going Away in Two Model Cycles | The Truth About CarsAfter all, I told Ruby, when electronic ignition, electronic fuel injection and digital engine control devices came in, enthusiasts were worried that they wouldn’t be able to tinker with cars for performance, but since then we’ve seen car guys go from changing carburetor jets to “chip tuning”, making changes to the way the car’s ECU operates the engine.
That’s when Ruby said, almost matter of factly, “Yeah, but all that’s going away. The open bus will be gone in two model cycles.” Automakers currently use something called the CAN bus. Years ago computer designers decided to use the word bus (from the Latin omnibus, “for all”) to describe something that lets one part of a computer to talk to another part of the computer. The Controller Area Network is a bus standard used by automakers to allow electronic devices in a car or truck to communicate with each other. Because it is an “open” bus that allows data to flow in both directions, the CAN bus is also what lets you plug your tuning gizmo into the OBD port and change the engine mapping.