Common Causes:
* Faulty Wheel Speed Sensor (WSS): This is the most frequent culprit. These sensors monitor wheel rotation speed. A faulty sensor will provide inaccurate data, triggering the ABS light. They can fail due to age, damage (from road debris or impacts), or corrosion. Each wheel has a sensor.
* Low Brake Fluid: While this usually triggers a separate brake warning light, low fluid can indirectly affect the ABS system and cause the light to illuminate.
* ABS Control Module (PCM/ABS Module): This is the "brain" of the ABS system. A faulty module can cause a variety of problems, including the ABS light staying on. This is a more expensive repair.
* Wiring Issues: Damaged, corroded, or loose wiring to the wheel speed sensors or the ABS module can disrupt the system and trigger the light. This is often overlooked.
* Faulty ABS Pump Motor: This motor is responsible for regulating brake pressure during ABS activation. If it fails, the ABS light will remain on.
* Faulty ABS Hydraulic Control Unit (HCU): This component contains the valves and other hydraulic components of the ABS system. A malfunction here is a more serious issue.
* ABS Ring (tone ring): Located on the wheel hub, the tone ring is what the wheel speed sensor reads. Damage to the tone ring (often from a hard impact) will prevent accurate readings.
Less Common Causes:
* Faulty Brake Switch: While less directly related, a faulty brake switch can sometimes affect ABS functionality.
Troubleshooting:
You should have the ABS system professionally diagnosed. A mechanic can use a scan tool to read diagnostic trouble codes (DTCs) from the vehicle's computer. These codes will pinpoint the specific problem. Simply replacing parts without a proper diagnosis could be expensive and ineffective.
Don't ignore the ABS light. While you can still brake, the ABS functionality is disabled, reducing your ability to maintain steering control during emergency braking situations on slippery surfaces. Getting it fixed is crucial for safety.
