300TE 4MATIC (124.290) L6-3.0L (103.985) (1991)
Wheel Speed Sensor: Description and Operation
FRONT WHEEL SENSOR
The sensor sends wheel speed information to the ECU where it's speed signals are used to determine when anti-lock control is required. Each wheel
speed sensor consists of a magnet surrounded by a coil of wire. Mounted next to each sensor is a toothed ring that rotates along with the brake disc.
As each tooth passes, the magnetic field in the wheel sensor is strengthened momentarily. This field strength change, repeated as each tooth passes the
sensor, induces voltage in the wheel speed sensor coil and coaxial cable. The ECU compares the frequency of the AC signals from the wheel speed
sensors to detect rapid wheel deceleration, indicating possible wheel locking.
CAUTION: Tire size determines the number of teeth on the front reluctor ring. It's therefore important that the vehicle be equipped with the original
equipment tire sizes. Changing tire size could affect system function.
NOTE: Always route these cables in exactly the same position as original manufacture. Electronic noise from improper cable routing can cause
improper signals to be sent to the ECU.
Front Axle Wheel Speed Sensors
REAR WHEEL SPEED SENSOR
Vehicles with ASR have a speed sensor on each of the four wheels.
The single-edged tooth (arrow) and the long cable with a coaxial plug (as on vehicles with ABS) identify the two front axle wheel speed sensors.
Left Rear Wheel Speed Sensor
The letter E (arrow) on the plug identifies the left rear wheel speed sensor (L6/3).