What Causes Wheel Speed Sensor Failure

What Causes Wheel Speed Sensor Failure In the contemporary automotive landscape, vehicles are equipped with an array of sensors, each serving a specific purpose. These sensors can be classified into subsets for clarity during discussions. One such subset is the category of speed sensors, crucial components in today’s vehicles.

Within this subset, various types of sensors deserve mention – engine speed sensors (crankshaft/camshaft position) and transmission speed sensors, each with distinct functions. However, the most common speed sensors that come to mind are those mounted at the wheel positions of a vehicle.

While modern wheel speed sensors are designed to be robust, they are not immune to occasional failures. This highlights the importance of recognizing symptoms linked to wheel speed sensor-related issues, as identifying the problem is the first step towards rectification.

Read on to delve into the symptoms associated with a malfunctioning wheel speed sensor and understand how to address such issues should they arise.

Unveiling the Function of a Wheel Speed Sensor

What Causes Wheel Speed Sensor Failure
What Causes Wheel Speed Sensor Failure

Whether referred to as a Wheel Speed Sensor (WSS) or ABS Sensor, this electrical component provides feedback regarding the rotational speed of an individual wheel on a vehicle. Distinct from a vehicle’s transmission speed sensor, which serves a different purpose, wheel speed sensors are typically magnetic. They generate measurable “pulses” as a hub-mounted tone ring rotates past their probes.

The frequency of these pulses correlates directly with the detected speed of the wheel, as interpreted by a vehicle’s software. More pulses within a specific timeframe signify a faster registered rotational speed of the wheel. Two configurations of wheel speed sensors exist:

  1. Passive Sensor: Analog in nature, this sensor type doesn’t require a reference voltage for operation.
  2. Active Sensor: Requires an input voltage and employs an encoder-style tone ring.

Modern vehicles mostly employ the latter due to its reliability. The vehicle’s software utilizes feedback from one speed sensor to compare with feedback from others on the same vehicle. This comparison helps detect wheel spin or potential brake lockup.

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Locating the Wheel Speed Sensor

What Causes Wheel Speed Sensor Failure
What Causes Wheel Speed Sensor Failure

Wheel speed sensors are mounted within the vehicle’s four hubs. Their position can be identified by tracing the electrical pigtail leading to their mounting point. This wiring often runs along the vehicle’s frame rail before connecting to brake hoses or the hub assembly of a specific wheel end.

The sensor is countersunk into its corresponding hub assembly, positioned closely to a hub-mounted tone ring. This arrangement ensures proper interfacing with the tone ring for accurate function.

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Detecting Symptoms of a Malfunctioning Wheel Speed Sensor

What Causes Wheel Speed Sensor Failure
What Causes Wheel Speed Sensor Failure

A faulty wheel speed sensor typically comes with several secondary symptoms, some more noticeable than others. Identifying these symptoms early is crucial for expedited repairs. Here are common signs:

1. ABS Light Illumination: A malfunctioning ABS sensor often triggers the illumination of the ABS warning light, indicating an ABS-related fault.

2. Disabled Active Safety Systems: Anti-lock brakes, stability control, and traction control rely on wheel speed sensor feedback. These systems are often disabled in the presence of a sensor malfunction.

3. Brake Pedal Pulsation: In rare cases, the brake pedal might pulsate as if an ABS-modulated brake application is occurring while driving.

4. Increased Stopping Distances: After wheel speed sensor failure, your vehicle might take longer to stop, particularly during emergency situations, due to disabled ABS functionality.

Read More : What Causes A Steering Wheel To Lock Up While Parked

Causes of Wheel Speed Sensor Failure

What Causes Wheel Speed Sensor Failure
What Causes Wheel Speed Sensor Failure

Several factors can lead to wheel speed sensor failure. Debris strikes from road materials, magnetic debris accumulation around the sensor, damaged wiring, or corrosion on the connector are common culprits. Damaged wiring or corrosion can increase resistance in the sensor circuit or even cause an open connection.

Cost of Wheel Speed Sensor Replacement

Replacement costs for wheel speed sensors vary based on vehicle make and model. Some manufacturers might charge more than others for the same sensor, and labor rates can also differ. On average, replacing a wheel speed sensor can range between $150 and $300.

The sensor’s cost constitutes around 1/3 of the total expense, while the remaining 2/3 covers labor charges.

Continuing to Drive with a Faulty Sensor

While it’s possible to continue driving with a compromised wheel speed sensor, it’s not advisable. Active safety systems like anti-lock braking, stability control, and traction control rely on these sensors for proper functioning. Driving with these systems disabled poses safety risks and potential liability in case of accidents.

Addressing a Wheel Speed Sensor Issue

It’s recommended to diagnose and repair a wheel speed sensor fault promptly. If you lack the expertise, seek help from a reputable service center. Mechanics use scan tools, oscilloscopes, or digital multimeters to diagnose faulty sensors and related issues. Visual inspections are also performed to identify visible damage or debris strikes. Proper diagnostics ensure optimal vehicle safety and performance.