Why do ABS sensors fail?
ABS wheel speed sensors fail primarily due to contamination, wiring and connector problems, physical damage or misalignment, and electrical faults that disrupt the signal to the ABS control module. When these issues occur, the ABS or stability control lights can illuminate, and braking performance may be affected.
Common failure modes
The following list highlights the most frequent ways ABS sensors stop working correctly, based on service data and everyday automotive repair experience.
- Contamination and fouling: Dirt, road grime, brake dust, oil leaks, or water can coat the sensor or tone ring, dampening or distorting the signal.
- Wiring and connector problems: Damaged, frayed, or corroded wires; loose or gapped connectors; and moisture intrusion can cause intermittent or no signal.
- Physical damage: Impacts from potholes, curbs, or road debris can crack or bend the sensor or tone ring (reluctor), or misalign them.
- Incorrect air gap or misalignment: The distance between the sensor and the tone ring is critical; wear, hub/apply changes, or improper installation can increase or reduce the gap, degrading signal quality.
- Sensor or tone ring wear: Worn or damaged tone rings or failing sensors (passive magnetic or active Hall-effect types) can produce irregular readings or no reading at all.
- Moisture and shorts: Water ingress or short circuits in the sensor circuit can cause intermittent fails or constant fault codes.
- Extreme temperatures and vibration: Prolonged exposure to heat, cold, or vibration can degrade insulation and electronics over time.
- Wheel bearing or hub issues: Worn bearings or loose hubs can alter alignment or create wobble that compromises the sensor’s signal.
- Control module or CAN-network faults: In some cases, faults in the ABS control module or related data networks can falsely indicate a sensor problem.
Most failures are not caused by a single fault but by a combination of wear, exposure, and installation conditions that gradually degrade the signal.
Diagnostic steps for ABS wheel speed sensors
Diagnosing ABS sensor problems involves a systematic approach to verify signal integrity, wiring health, and mechanical alignment before replacing components.
- Retrieve fault codes with an OBD-II scanner to identify which wheel or circuit is implicated and whether the codes indicate a “No Signal,” “Circuit Malfunction,” or intermittent issue.
- Visually inspect wiring, connectors, and the sensor itself for corrosion, abrasion, water intrusion, or damage to the loom and harness routing.
- Check the air gap between the sensor and the tone ring and inspect the tone ring for cracks, missing teeth, or excessive wear.
- Test sensor resistance (for passive sensors) and verify proper operation with a multimeter or oscilloscope; compare readings to manufacturer specifications.
- Observe live wheel-speed data while spinning each wheel to detect erratic or absent readings; swap sensors or tone rings to pinpoint the faulty component.
- Inspect related components such as wheel bearings and hub assemblies that could affect sensor alignment or signal quality.
Accurate diagnostics help distinguish a bad sensor from wiring issues or a failing ABS control module, guiding appropriate repair rather than guesswork.
Prevention and maintenance tips
Preventive measures can extend sensor life and reduce the likelihood of ABS faults, especially on vehicles with high mileage or challenging road conditions.
- Regularly inspect sensor and harness routing during brake or wheel work; look for chafed wires, loose connectors, and signs of moisture.
- Keep sensors and tone rings clean from brake dust, oil, and road grit using gentle cleaners and avoid harsh solvents that could damage seals.
- Avoid impact damage by careful driving on rough roads and when removing or installing wheels; recheck torque after maintenance.
- Use OEM or high-quality replacement sensors and tone rings; improper parts can lead to incorrect spacing or signal issues.
- Ensure proper alignment and correct air gap during installation; reseat or recalibrate as specified by the vehicle manufacturer.
- Protect wiring from heat, salt, and moisture by securing looms and using protective grommets and loom tape where appropriate.
By maintaining clean, well-routed wiring and correctly installed sensors, most ABS-related faults can be prevented or identified early during routine service.
Summary
ABS sensor failure commonly stems from contamination, wiring/connectors, physical damage, misalignment, and general electrical faults. Diagnosis relies on fault codes, visual inspection, gap and tone ring checks, and signal testing, while preventive maintenance—careful installation, clean components, and robust wiring protection—significantly reduces the risk of failure and keeps ABS functioning as designed.
What causes an ABS sensor to go out?
Ring can cause the sensor to send inaccurate. Or erratic data to the ABS. Control module. The third cause is internal short circuits electrical issues within the sensor.
Is it okay to drive with a bad ABS sensor?
You can likely drive with a bad ABS sensor, but you should do so with extreme caution, drive carefully, and get it fixed as soon as possible. Your regular brakes will still work, but the anti-lock feature will not engage during hard braking, potentially increasing stopping distances and making it harder to steer. If the red brake warning light also comes on, do not drive the car, as it could indicate a more serious problem with the conventional braking system.
What to do
This video explains the symptoms of a bad ABS sensor: 45sDr. Cool YouTube · Jan 14, 2024
- Drive carefully: Avoid sudden stops and maintain extra distance from other vehicles.
- Check for other warning lights: If the red brake warning light is also on, pull over safely and do not drive the car. Arrange for a tow to a mechanic.
- Consider a reset: Turn off the engine, wait a moment, and then restart the car. This can sometimes resolve minor glitches.
- Schedule a repair: If the light stays on, have a mechanic diagnose the issue and replace the faulty sensor to restore your anti-lock braking system.
Why it's risky
- Loss of anti-lock function: In a panic stop, your wheels could lock up, causing you to lose steering control.
- Increased stopping distance: The inability of the ABS to prevent wheel lock-up can lengthen your stopping distance.
- Potential for greater damage: Ignoring the problem could lead to more serious issues with the entire braking system or other related electronic modules.
What are the three common causes of sensor failure?
These faults can arise from various issues, such as physical damage, electrical problems, environmental factors, or software errors. A faulty sensor cannot perform its function properly but instead may provide false information for decisions, thus making the system unreliable.
What is the life expectancy of an ABS sensor?
ABS sensors can last anywhere from 60,000 to 150,000 miles or 5 to 10 years, but their lifespan depends heavily on driving conditions, with factors like road salt, debris, and heat potentially causing premature failure. In many cases, these sensors are designed to last the lifetime of the vehicle, and their failure is often due to external damage rather than age.
Factors that influence ABS sensor lifespan
- Environmental conditions: Sensors in areas with road salt, frequent rain, or excessive dust are more prone to corrosion and damage.
- Road conditions: Driving on rough roads or roads with a lot of debris can cause physical damage to the sensor or its wiring.
- Physical damage: Direct impact from road debris can damage the sensor or its components.
- Heat exposure: The sensor's proximity to the engine can cause the internal wiring to become brittle over time.
Signs of a failing ABS sensor
- The ABS warning light on your dashboard is illuminated.
- Inaccurate speedometer readings.
- The anti-lock brakes feel less effective or lock up.
