Town & Country V6-3.8L VIN L (2006)
Wheel Speed Sensor: Description and Operation
ABS SWITCHES/SENSORS
Master Cylinder: The master cylinder is a standard tandem compensating port design for ABS and non ABS systems. Traction control vehicles use a
dual center port master cylinder. For proper traction control operation the standard master cylinder must not be used.
A fluid level switch is located in the master cylinder fluid reservoir. The switch closes when a low fluid level is detected. The fluid level switch turns
on the brake warning indicator by grounding the indicator circuit. This switch does not disable the ABS system.
Wheel Speed Sensors and Tone Wheels: One active wheel speed sensor (WSS) is located at each wheel. The sensors use an electronic principle
known as magneto-resistive to help increase performance, durability and low speed accuracy. The sensors convert wheel speed into a small digital
signal. A toothed gear tone wheel serves as the trigger mechanism for each sensor.
The CAB/ABM sends 12 volts to power an Integrated Circuit 01C) in the sensor. The IC supplies a constant 7 mA signal to the CAB/ABM. The
relationship of the tooth on the tone wheel to the permanent magnet in the sensor, signals the IC of the sensor to toggle a second 7 mA power supply
on or off. The output of the sensor, sent to the CAB/ABM, is a DC voltage signal with changing voltage and current levels. The CAB/ABM monitors
the changing amperage (digital signal) from each wheel speed sensor. The resulting signal is interpreted by the CAB/ABM as the wheel speed.
Because of internal circuitry, correct wheel speed sensor function cannot be determined by a continuity or resistance check through the sensor.
Correct antilock system operation is dependent on tone wheel speed signals from the wheel speed sensors. The vehicle's wheels and tires should all be
the same size and type to generate accurate signals. In addition, the tires should be inflated to the recommended pressure for optimum system
operation. Variation in wheel and tire size or significant variations in inflation pressure can produce inaccurate wheel speed signals; however, the
system will continue to function when using the correct factory mini-spare.