ABS System Related:
* ABS Module Failure: This is a common culprit. The ABS module is the "brain" of the system and its failure can trigger both warning lights. It's an expensive repair often requiring replacement.
* Wheel Speed Sensor (WSS) Malfunction: Each wheel has a sensor that measures its rotation speed. A faulty sensor, wiring issue to the sensor, or a damaged sensor ring (located on the wheel hub or axle) will prevent the ABS from functioning correctly and trigger the lights. This is a relatively common and usually less expensive repair than the module.
* ABS Hydraulic Control Unit (HCU) Problems: This unit manages the hydraulic pressure for the ABS system. Internal leaks or failures within the HCU can cause the lights to come on. Repair or replacement is typically expensive.
* Low Brake Fluid: While seemingly unrelated, low brake fluid can trigger both lights. The system may detect a leak or pressure issue. *Check your brake fluid level immediately!* This is the cheapest and easiest thing to check first.
* Wiring Issues: Damaged, corroded, or disconnected wiring within the ABS system can cause intermittent or constant illumination of the warning lights. This can be tricky to diagnose.
Brake System Related (Even if ABS Light is on):
* Low Brake Fluid (again!): As mentioned, this is critical. Low fluid indicates a leak somewhere in the braking system, a serious safety concern.
* Brake Master Cylinder Failure: The master cylinder is responsible for delivering pressure to the brakes. A failure can lead to reduced braking power and illuminate the brake light, which can subsequently trigger the ABS light as well.
* Brake Light Switch: A malfunctioning brake light switch can cause the brake light to stay on, and this can sometimes also trigger the ABS light.
Diagnostics:
You'll need to diagnose the problem. Options include:
* OBD-II Scanner: A code reader can read diagnostic trouble codes (DTCs) stored by the vehicle's computer. These codes often pinpoint the problem. A basic scanner may not cover ABS codes, an advanced scanner is needed.
* Professional Mechanic: A mechanic with experience in brake systems and ABS diagnostics is the best option. They have the tools and expertise to accurately diagnose and repair the issue.
Important Safety Note: Driving with the ABS and brake lights illuminated means your ABS system is not functioning. While you can still brake, you'll lose the anti-lock functionality, making it harder to control the vehicle during emergency braking, especially on slippery surfaces. It is strongly recommended to get this fixed as soon as possible. Driving with a brake system problem is dangerous and illegal in many areas.
