Wheel RPM sensor, component description - GF42.45-P-5134RC
MODEL 171.4 as of model year 09 /YoM 08 model refinement package
Shown on front axle L6/1 Left front RPM sensor; L6/2 Right front RPM sensor; L6/3 Left rear RPM sensor; L6/4 Right rear RPM sensor.
Location The front RPM sensors are mounted on the left and right front axle steering knuckles. The rear RPM sensors are mounted on the left and right wheel carriers of the rear axle.
Task Standstill, direction of rotation and RPM of the wheels are recorded via the RPM sensors. The signals of the RPM sensors are read in discretely by the ESP and BAS control unit (N47-5).
Function The RPM sensor is a magnetoresistive sensor element (active wheel RPM sensor) and changes its resistance depending on the magnetic field applied to it externally (multipole ring on wheel).
The ESP and BAS control unit measures the current it supplies to the RPM sensor. Depending on the position of the multipole ring (negative pole or positive pole), a current strength of I =7 mA or I = 14 mA is measured, producing a square wave signal. The ESP and BAS control unit derives the wheel speed from this square wave signal.