Wheel Pulse (Speed) Sensors
WARNING: This page is about a different car, the 2004 BMW X5, 2003 BMW X5, 2002 BMW X5, 2001 BMW X5, and 2000 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.
Wheel pulse (speed) sensors are installed at each wheel. Each wheel pulse sensor generates a signal proportional to the speed of a rotating toothed wheel. Wheel pulse sensors relay the signal to the ABS/ASC+T control module, which computes the actual wheel speed. The toothed wheels, which run past the permanently magnetized edge of the speed sensor, are attached to the hub.