* Low Brake Fluid: This is the most common and simplest cause. Check your brake fluid reservoir. Low fluid indicates a leak somewhere in the system (brake line, caliper, wheel cylinder, etc.) which needs immediate attention.
* ABS Module Failure: The ABS (Anti-lock Braking System) module is a computer that controls the ABS function. A faulty module can trigger both lights. This is a more expensive repair, often requiring replacement.
* ABS Wheel Speed Sensor Issues: These sensors monitor the speed of each wheel. A faulty sensor, wiring problem to the sensor, or even a damaged sensor ring (located on the wheel hub) can cause the lights to illuminate. These are relatively common and usually require replacing the sensor itself.
* Brake Light Switch Failure: While less common when both lights illuminate, a faulty brake light switch can sometimes cause both lights to come on. This switch is crucial for activating the brake lights and also sends a signal to the computer related to braking.
* Master Cylinder Problems: A failing master cylinder can cause low brake fluid or an inconsistent brake pedal feel, leading to the warning lights.
* Wiring Issues: Damaged or corroded wiring within the braking system, especially related to the ABS module or wheel speed sensors, can interrupt signals and trigger the warning lights.
* Brake Pressure Sensor Failure: A faulty brake pressure sensor can send incorrect readings to the ABS module.
* Faulty ABS Pump Motor: In some rare cases the ABS pump motor itself may fail.
What to do:
1. Check Brake Fluid: This is the first and easiest thing to do. If it's low, immediately find and fix the leak before driving further.
2. Have it Diagnosed: The best approach is to get your Trailblazer scanned with an OBD-II code reader. This will give you diagnostic trouble codes (DTCs) that will pinpoint the specific problem. A mechanic with experience on older GM vehicles is recommended. Generic OBD-II readers may not access all ABS system codes on older vehicles.
Ignoring these warning lights is dangerous. Driving with malfunctioning brakes can lead to serious accidents. Get your vehicle checked by a mechanic as soon as possible.
