ABS warning light stays on

Symptoms

• ABS light stays on continuously on the dash
• Traction control light may also be on
• Brakes feel normal but the warning persists
• Light appeared after hitting a pothole or curb

Likely causes

• CommonFaulty wheel speed sensorThese sensors detect wheel rotation for ABS and can fail or get dirty/damaged.
• CommonDamaged wiring or connector to a speed sensorWiring near the wheels is exposed to road debris and can get damaged, especially after hitting a curb or pothole.
• PossibleLow brake fluid levelSome systems tie the ABS light to brake fluid level as a safety check.
• PossibleFaulty ABS module or pumpThe control module or hydraulic pump for the ABS system can develop internal faults.

What to do

1. Check the brake fluid reservoir level under the hood and top off if low with the correct fluid type.
2. Have the ABS system scanned with a code reader, since a check engine light scanner may not read ABS-specific codes.
3. Inspect visible wheel speed sensor wiring near each wheel for damage, especially if the light appeared after hitting something.
4. Note if the light came on gradually or suddenly after a specific event like a pothole or curb strike.
5. Avoid ignoring the ABS light, since it means anti-lock braking may not function in an emergency stop even though normal brakes still work.
6. Have a shop clean or replace a faulty wheel speed sensor if that's what the code points to.
7. Get brakes fully inspected if the ABS light is paired with any change in brake pedal feel.
8. Have the ABS module tested if sensors and wiring check out fine.

Tools and parts

• OBD-II code reader (ABS capable)
• Flashlight

When to call a pro

ABS diagnosis needs a scanner that reads ABS-specific codes, which most basic code readers don't cover; a shop can pinpoint the exact sensor or module at fault.

Safety