ABS WHEEL-SPEED SENSOR AND ABS SENSOR ROTOR CONSTRUCTION/OPERATION

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Construction

Front

  • The front ABS wheel-speed sensor utilizes a semi-conductor element that contains an active drive circuit (MR element*). The front sensor is installed on the front wheel hub.
  • The front 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 front 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 is possible that the voltage from the tester could damage the semiconductor inside the ABS wheel-speed sensor. Inspect using the 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

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

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Operation

Front

  • As the front ABS sensor rotor rotates, the magnetic flux between the front ABS wheel-speed sensor and the front 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 ABS HU/CM.
  • For every single rotation of the ABS sensor rotor, 44 rectangular wave pulse signals are output. The CM in the ABS HU/CM calculates the wheel speed from the periodicity of these pulses.

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Rear

  • 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 CM part of the ABS 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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