Originally Posted by
tunerpro
GM's "Global B" electrical architecture is meant to plug all the remote access security holes of the type you're referring to by not only isolating critical safety system networks from other networks but also by making each vehicle's communications unique. Even if you knew how to hack the network the engine controller is on, you wouldn't be able to reach it from, say, an exploit in the radio software (like the FCT remote hack). But even if you could, you would only know how to send the messages based on the ONE vehicle you looked at. If you looked at 1000 of them, they would all be different with no discernible pattern.
For these same reasons, nothing that is Global B (C8, 2020+ CT4/CT5, 2021+ full size SUV at the time of writing, more to come with certainty) would have a remote possibility of working with a non-factory standalone engine controller unless you found yourself in possession of information that GM obviously wouldn't want you to know (at which point you can expect to be hauled into court to explain yourself).
Even "piggy backs" are going to be more difficult to create in the future now that they're moving to digital communications on most engine sensors. For example, the newest vehicles use a "LIN" based digital sensor for the IAT sensor. No more messing with resistors to change timing curves, you need to spoof an entire digital protocol, complete with rolling integrity checks in order to spoof the ECM. Turbochargers are now using electric wastegates now instead of pressure based wastegates which are essentially the same type of device that you have for a throttle body, complete with position sensors, digital protocol and diagnostics. They've hardened just about every signal and communication path possible on these new vehicles.