What does an erratic waveform from a wheel speed sensor typically indicate?

• A. Sensor air gap is excessive
• B. Worn brake pads
• C. Electrical issues in the wiring
• D. Tone ring is probably damaged

Answer: (D)

An erratic waveform from a wheel speed sensor generally indicates that the sensor is not receiving a consistent signal, leading to variable readings. This can often be traced back to issues with the tone ring, which is responsible for generating the magnetic field that the sensor detects. If the tone ring is damaged—such as having missing teeth or being contaminated—then the sensor will struggle to produce a steady signal, resulting in the observed erratic waveform. This inconsistency can severely affect the performance of systems that rely on accurate wheel speed readings, such as anti-lock brakes and traction control systems.

Other factors such as sensor air gap, worn brake pads, or electrical wiring issues may also cause problems, but they typically do not produce the same kind of erratic signal that indicates a direct problem with the tone ring.