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PEX Aftermarket ABS Sensors & Extension 

Purpose and Function:

 

An ABS sensor, also known as a wheel speed sensor, monitors how fast each wheel is turning and sends this information to the ABS or stability control system. This allows the vehicle to prevent wheel lock-up during hard braking and maintain traction.


There are two main sensor types:

  • Passive (inductive): Generates its own AC signal from a toothed tone ring.

  • Active (Hall-effect or magnetoresistive): Uses an external power supply and produces a digital square-wave signal that works accurately even at zero speed.

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Features & benefits

  • Provides real-time, precise wheel speed data for ABS, traction, and stability systems.

  • Fast and accurate from 0 rpm to highway speeds.

  • Highly durable, designed to withstand heat, vibration, dirt, and moisture.

  • Plays a direct role in improving braking performance and vehicle safety.

  • Modern versions are often integrated into hub bearings, reducing installation time and improving reliability.

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Technical Highlights

  • Signal type:

    • Passive sensors produce a sinusoidal AC voltage that increases with wheel speed.

    • Active sensors create a clean square-wave signal whose frequency matches wheel rotation.

  • Typical readings:

    • Passive coil resistance: around 500–2,500 ohms (varies by vehicle).

    • Active sensor supply: approximately 5–12 volts.

  • Sensor gap: Maintain between 0.4–1.8 mm or as specified by the manufacturer.

  • A damaged or dirty tone ring can distort signals and trigger ABS faults.

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Diagnostic and Testing Tips

  • Visual check: Inspect the tone ring, wiring, and connectors for corrosion, damage, or buildup.

  • Resistance or voltage check:

    • For passive sensors, verify correct coil resistance.

    • For active sensors, confirm supply voltage at the connector.

  • Dynamic test: Spin the wheel while viewing the sensor output on an oscilloscope.

    • Passive sensors show a smooth sine wave.

    • Active sensors show square pulses.

  • Scan tool verification: Compare wheel-speed readings between sides; inconsistencies indicate a fault.

  • Repair damaged wiring first, clean the tone ring, and replace the sensor only if necessary.

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Installation Tips and Common Issues

  • Always set the correct air gap and torque when fitting sensors.

  • Keep cables clear of moving or hot parts and ensure connectors are sealed properly.

  • Some two-wire sensors are active types—don’t rely on wiring alone to identify them.

  • Static resistance checks aren’t enough; dynamic tests give real results.

  • A cracked or corroded tone ring is just as likely to cause ABS faults as a bad sensor.

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