Pulse Sensors
WARNING: This page does not describe the selected car, but rather 21 other vehicles, including the 2003 BMW M5, 2003 BMW 540i, 2003 BMW 530i, 2003 BMW 525i, and 2002 BMW M5. However, it is still accessible from the selected car via links, so may be relevant.
Pulse sensors are installed at each wheel. Pulse sensors measure the rate at which teeth on pulse wheel rotate. The sensors then relay signal to the ECU, which computes actual wheel speed. Pulse wheels, which run past permanently magnetized edge of pulse sensor, are attached to hub.