* ABS Sensor Issues: The most common reason is a problem with the rear wheel speed sensors. These sensors are crucial for the ABS system to function correctly. During the brake job, you might have:
* Dislodged a sensor: The sensors are delicate and easily damaged or dislodged if bumped or knocked during the repair. They may be slightly misaligned, dirty, or have a broken wire.
* Damaged the sensor wiring: You could have pinched, cut, or otherwise damaged the wiring harness leading to the sensor.
* Low Brake Fluid: While less likely if you bled the system properly, low brake fluid can trigger these warning lights. Check your brake fluid reservoir level. If it's low, you likely have a leak somewhere in the system.
* Air in the Brake Lines: If the system wasn't properly bled after the replacement, air in the lines can cause erratic sensor readings and trigger the lights. Bleeding the brakes is crucial after any brake work. If you only bled one rear wheel, it was still not properly bled. Air trapped in other parts of the system can also cause issues.
* Brake System Malfunction (Less Likely): Although you've worked on the rear brakes, a problem elsewhere in the braking system (e.g., a failing master cylinder, proportioning valve issue) could be causing the lights, especially if the issue existed prior to your work.
* Parking brake switch: If the parking brake switch is misaligned or damaged, it could trigger these lights.
Troubleshooting Steps:
1. Check Brake Fluid Level: Make sure the fluid reservoir is filled to the correct level. A low level indicates a leak somewhere.
2. Re-check ABS Sensor Connection and Cleanliness: Carefully examine both rear wheel speed sensors. Make sure they're securely plugged in, clean, and not damaged. Clean them with a wire brush if necessary.
3. Re-bleed the Brakes: Thoroughly bleed all four brake calipers to ensure there's no air in the lines. This is a crucial step and should be done correctly using a pressure bleeder or a helper.
4. Inspect Wiring: Visually inspect the wiring harnesses leading to the ABS sensors for any signs of damage, cuts, or loose connections.
5. Check the Parking Brake Switch: Make sure the parking brake switch is functioning correctly.
6. OBD-II Scanner: Use an OBD-II scanner to read the trouble codes from the vehicle's computer. This will give you a more precise indication of the problem. The code will likely point to a specific sensor or system issue.
If you've tried these steps and the lights remain on, it's best to take your vehicle to a qualified mechanic for diagnosis and repair. Improperly functioning brakes are a serious safety hazard.
