What is ABS Wheel Sensor?

The ABS wheel speed sensor, also known as the wheel speed sensor or ABS sensor, is a critical component of the ABS system. Its primary function is to monitor the rotational speed of each wheel and provide this information to the ABS control module and other vehicle dynamics systems.

If the ABS module detects any of the wheels slowing too rapidly during a hard braking maneuver, the hydraulic control unit will automatically use its isolation solenoids to block brake fluid pressure to any or all wheels that are beginning to slide, which helps keep you in control of the vehicle.

Where is ABS Wheel Sensor Located?

The ABS wheel speed sensors are typically located near each wheel hub or axle. They are positioned very close to a toothed wheel, often called a tone ring or reluctor ring, which is attached to the wheel hub or axle.

Bad ABS Wheel Sensor Symptoms

A malfunctioning ABS Wheel Sensor can manifest in various symptoms, indicating potential issues with the vehicle’s performance:

  1. ABS Warning Light illuminated: When the ABS warning light remains illuminated on the dashboard, it indicates a problem within the ABS system. A malfunctioning ABS wheel sensor is a common cause for this light to come on, signaling that the ABS system is not functioning properly.
  2. Wheel Lock-Up During Hard Braking: Without accurate wheel speed data from the ABS wheel sensor, the ABS system cannot prevent wheel lock-up effectively. As a result, wheels may lock up during hard braking, leading to loss of vehicle control.
  3. Longer Stopping Distances: With a faulty ABS wheel sensor, the ABS system may not activate properly during hard braking, leading to longer stopping distances and reduced braking performance.
  4. Traction Control Light illuminated: Many modern vehicles use the ABS wheel speed sensors for traction control systems. A faulty sensor can cause the traction control warning light to illuminate. Resulting in decreased vehicle stability during acceleration and cornering.
  5. Hill Hold Control Warning Light illuminated: Many modern vehicles use the ABS wheel speed sensors for Hill Hold Control. A faulty ABS wheel speed sensor can cause the Hill Hold Control warning light to illuminate, indicating that the system is not functioning properly.
  6. Diagnostic Trouble Codes (DTCs): A scan of the vehicle’s onboard diagnostics system (OBD-II) may reveal specific trouble codes related to the ABS wheel speed sensors, indicating which sensor is malfunctioning. The retrieved trouble codes will indicate the exact nature and location of the problem.

Common ABS Wheel Sensor fault codes

Here is a list of codes that are associated with the bad ABS Wheel Sensor:

  • Left Front Wheel
    • C0035: Left Front Wheel Speed Circuit Malfunction
    • C0036: Left Front Wheel Speed Sensor Circuit Range/Performance 
  • Right Front Wheel
    • C0040: Right Front Wheel Speed Circuit Malfunction
    • C0041: Right Front Wheel Speed Sensor Circuit Range/Performance 
  • Left Rear Wheel
    • C0045: Left Rear Wheel Speed Circuit Malfunction
    • C0046: Left Rear Wheel Speed Sensor Circuit Range/Performance
  • Right Rear Wheel
    • C0050: Right Rear Wheel Speed Circuit Malfunction
    • C0051: Right Rear Wheel Speed Sensor Circuit Range/Performance

What Causes the Malfunction of ABS Wheel Sensor ?

Causes of a Faulty ABS Wheel Sensor

  1. Mechanical Damage: Physical damage to the sensor or its components can impair its ability to function correctly. This can result from impacts, vibrations, or improper handling during maintenance.
  2. Break in the Tone Ring: The tone ring, or reluctor wheel, works with the ABS wheel sensor to provide accurate wheel speed readings. Cracks or breaks in the tone ring can cause the sensor to send inaccurate or erratic data to the ABS control module.
  3. Internal Short Circuits: Electrical issues within the sensor itself, such as short circuits, can prevent it from sending correct signals to the ABS Control Module.
  4. Electrical issue: Poor connections across electrical connectors, broken wiring, blown fuses, loss of ground, or issues with previously repaired wires can disrupt the connection with the ABS Wheel Sensor.

Other Issues That Exhibit Similar Symptoms as a Bad ABS Wheel Sensor

When a car exhibits the symptoms mentioned above, and the ABS Wheel Sensor has been checked and found to be in working order but the issue persists, it’s essential to inspect the other components of the engine timing system.

  1. Malfunctioning ABS Control Module: The ABS control module processes the signals from the wheel speed sensors and controls the anti-lock braking system. If the control module is faulty, it may not interpret the sensor signals correctly, leading to the ABS light being illuminated and loss of anti-lock braking function.
  2. Faulty ABS Hydraulic Control Unit Valves: The ABS system includes solenoid valves that control brake fluid pressure to prevent wheel lock-up. If these valves become stuck or fail, they can cause issues similar to a bad wheel sensor, such as reduced braking performance and ABS warning lights.
  3. Faulty ABS Pump: The ABS pump maintains hydraulic pressure in the brake lines during ABS activation. A malfunctioning pump can result in inadequate brake fluid pressure, causing the ABS system to fail and triggering warning lights on the dashboard.

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