The tire pressure monitor started with MY07 E60 cars. Prior year cars have the flat tire monitor, which uses relative rotational speed of the 2 wheels on each axle.CarlK920 said:Apparently this is a newer system used on 05 and later models. My 04 has a system which uses relative tire rotation speed. I've switched out to winter tires with 17" wheels vs. 18" stock sport -- and back, and the system appears to initialize and work. (My manual also confirms the "relative speeds of the wheels" methodolgy.) Of course I also read a test in a car mag that showed this "relative speed" method was not all that effective. So, it sounds like you folks got a better system, albeit one that makes wheel swaps more difficult!