At each of the 4 wheels, there is an ABS sensor, the only thing with wires on it near the wheel. There is a spinning part of the axle or brakes that has notches in it, the sensor detects the magnetic change as the gaps spin past. If there is rust build up, or a problem with the sensor, that "could" cause a malfunction. This "should" also cause the spoiler to raise, but if you have a SRT6, obviously not. It is covered in page 5-332 of the 2005 service manual,