Curiously enough, I spent a year and a half working on gadgets that plugged into OBDII ports and read trouble codes. The EPA tests are government mandated and and they are supposed to work in a specified manner so they are testable anywhere. The extra private test functions (eg. oil life remaining) are proprietary and can work any way the manufacturer wants. The OBDII protocol is polled; they can tell when it's plugged in to a tester. The conclusion is obvious. The germans have a LOT of proprietary tests and other functions.