Comment by 27183

Reading codes is only part of it. For the last quarter century or so (some manufacturers more than others) if you replace certain components (radio, any computer module) you need to update the ECU to recognize the new component. This requires proprietary software and in many cases proprietary hardware as well. These "features" are marketed as an "anti-theft" mechanism. This renders some repairs basically impossible for the end user to perform.

The fact that they've been allowed to build systems like that is appalling.