ABS WHEEL-SPEED SENSOR CONSTRUCTION/OPERATION

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Construction

Front

  • The front antilock brake system (ABS) wheel-speed sensor is installed on the steering knuckle and the rear ABS sensor rotor is integrated with the drive shaft. Therefore, if there is any malfunction on the front ABS sensor rotor, replace the drive shaft.

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Rear (2WD)

  • The rear ABS wheel-speed sensor utilizes a semi-conductor element that contains an active drive circuit (MR element*). The rear sensor is installed on the rear wheel hub.
  • The rear ABS sensor rotor utilizes a magnetic encoder system that functions with magnetic rubber, and is integrated into the wheel hub component. Therefore, if there is any malfunction of the rear ABS sensor rotor, replace the wheel hub component.

*: A magneto-resistive force means that an exterior magnetic field acts on the element, changing the resistance of the element.

  Caution
  • When inspecting the ABS wheel-speed sensor, do not use a tester to inspect resistance. It impossible that the voltage from the tester could damage the semiconductor inside the ABS wheel speed sensor. Inspect using the parameter identification (PID) data monitor of the Mazda Modular Diagnostic System (M-MDS).

  Note
  • Magnetic encoder: A plate that has positive and negative poles (marked out) in a continuous, alternating line.

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Rear (4WD)

  • The rear ABS wheel-speed sensor is installed on the rear knuckle and the rear ABS sensor rotor is integrated with the rear drive shaft. Therefore, if there is any malfunction on the rear ABS sensor rotor, replace the rear drive shaft.

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Operation

Front and rear (4WD)

  • As the ABS sensor rotor rotates, magnetic flux formed from the permanent magnet varies and alternating current is formed with an electromagnetic conductor. Using this alternating current, rotation speed is expressed as a varying proportional cycle and from detection of this cycle the control module (CM) part of the dynamic stability control (DSC)/roll stability control (RSC) hydraulic unit (HU)/CM can then detect the wheel rotation speed. While the structures of the front and rear ABS wheel-speed sensor differ, the operation is the same.

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Rear (2WD)

  • As the rear ABS sensor rotor rotates, the magnetic flux between the rear ABS wheel-speed sensor and the rear ABS sensor rotor change periodically. This periodic change is in proportion to the rotation speed.
  • The semiconductor element in the wheel speed sensor detects the change in magnetic flux, and the active drive circuit converts it to a rectangular wave signal for the current, which is transmitted to the DSC/RSC HU/CM.
  • For every single rotation of the ABS sensor rotor, 44 rectangular wave pulse signals are output. The CM in the DSC/RSC HU/CM calculates the wheel speed from the periodicity of these pulses.

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