* Wheel Speed Sensors: This is the most common culprit. During the brake job, the sensors (located near the wheel hub) might have been bumped, damaged, disconnected, or their wiring disturbed. Even a small amount of debris on the sensor can interfere with its operation.
* ABS Ring/Tone Ring: The wheel speed sensor reads a tone ring (a toothed metal ring) on the wheel hub. This ring can become damaged, corroded, or even get bent slightly during a brake job. If the ring is damaged the sensor won't be able to read wheel speed accurately.
* Wiring Harness: The wiring to the wheel speed sensors can be damaged or corroded. A pinched wire or a loose connection will cause issues.
* ABS Module: While less likely after a simple brake job, it's possible the ABS module itself has a fault. This is less common and often requires professional diagnosis.
* Low Brake Fluid: Although you changed the pads/shoes, extremely low brake fluid could trigger the ABS light because it's part of the overall braking system's health monitoring. However, this is unlikely if you had sufficient fluid before and during the work.
* Air in the ABS System: Improper bleeding of the brakes could leave air in the ABS system. ABS bleeding is often different and more complex than regular brake bleeding.
What to Do:
1. Check the Obvious: Carefully inspect all four wheel speed sensors and their wiring. Make sure they are securely plugged in and not damaged. Clean them thoroughly with a sensor cleaner.
2. Inspect the Tone Rings: Examine the tone rings on the wheel hubs for any damage. They should be smooth and undamaged.
3. Check Brake Fluid Level: Ensure the brake fluid level is correct in the master cylinder reservoir.
4. Properly Bleed the Brakes: If you haven't already, ensure the brakes are correctly bled, including the ABS system if necessary (this might require a pressure bleeder and specific ABS bleeding procedure).
5. Use an OBD-II Scanner: An OBD-II scanner can retrieve ABS system diagnostic trouble codes (DTCs). This will pinpoint the exact problem. Many inexpensive OBD-II scanners are available.
If you're not comfortable with these steps, take your car to a qualified mechanic. They have the tools and expertise to diagnose and fix the problem correctly. Attempting to fix an ABS system without the proper knowledge can lead to further complications.
