What Causes the Brake System Warning Light to Illuminate?

[LeWalter]

Reasons for the brake system warning light to illuminate: 1. ABS function failure; 2. Severe wear or complete failure of brake pads; 3. Non-compliant brake fluid. Abnormalities in the brake system manifest as poor or ineffective braking, unilateral braking deviation, braking noise, brake drum overheating due to brake drag, or parking brake failure. The automotive brake system refers to a series of specialized devices that apply a certain force to specific parts of the vehicle (primarily the wheels) to enforce a certain degree of braking. The functions of the brake system are: to forcibly decelerate or even stop a moving vehicle as required by the driver; to ensure a stationary vehicle remains stable under various road conditions (including on slopes); and to maintain a stable speed for a vehicle moving downhill.

[StArya]

A few days ago, the brake light on my car suddenly came on, which scared me so much that I immediately pulled over. Upon checking, I found that the most common causes are usually one of three things: the brake fluid reservoir level is too low (you can check this yourself by looking at the indicator lines), the brake pads are worn to their limit (you can hear a metal grinding noise if you roll down the window), or the ABS sensor is covered in mud (especially common after rain). If you've just had the brake pads replaced, it might be that the mechanic forgot to reset the maintenance reminder. But the most worrisome scenarios are a brake fluid leak or ABS pump failure—these require calling a tow truck immediately. Remember, never keep driving when this light is on. My neighbor didn’t take it seriously last time, and when he pressed the brake pedal all the way down, there was no response—he almost rear-ended a truck.

[Abigail]

After 15 years of car repair experience, I've found that brake warning light issues can be addressed at three levels. Beginners should first check brake fluid - if the level is below the MIN line, simply top up with DOT4 specification fluid. For older vehicles, focus on whether the handbrake is fully released, as poor contact in the small switch beneath the handbrake lever can also trigger warnings. Third-level problems are more complex, such as a faulty wheel speed sensor (accompanied by wheel knocking sounds), ABS computer errors (occasionally resolved by restarting the vehicle), or a stuck brake pressure distribution valve (causing the car to pull to one side when braking). I recommend keeping an OBD diagnostic cable handy - for just a few dozen yuan, you can read specific trouble codes yourself, avoiding inflated quotes from repair shops.

[AdalynnFitz]

Last week, my little Fit suddenly had the brake light come on, and I figured out some tips. First, don't panic—press the brake pedal firmly a few times to feel the resistance. If it becomes stiff, it might be a vacuum hose leak. Then check the dashboard for any accompanying warnings, like if the tire pressure light also comes on, it could be a wheel speed sensor issue. Modified cars require extra attention—my aftermarket brake master cylinder brace was squeezing the fluid level sensor, causing false alerts. In city traffic, you can drive slowly under 40km/h to reach a repair shop, but if you smell burning or the brake pedal feels spongy, pull over immediately and call for roadside assistance. Finally, remember that this light may briefly illuminate after driving through water, which is normal—it should turn off once the water dries.

[McGrace]

Last month, the brake light came on while driving my child to school. Sharing a mom's experience on handling it: immediately turned on the hazard lights, slowed down, and found the nearest auto repair shop (searching 'brake repair' on the phone map was faster than going to a 4S shop). The inspection followed four steps: check if the floor mat was stuck under the brake pedal (my dog's mischief), feel the wheel hub temperature for any abnormality (a single overheated wheel indicates a stuck caliper), listen for any abnormal clicking noise when ABS activates (only audible on quiet roads), and finally check the maintenance records to see if the brake fluid hadn't been changed for over 20,000 km. Never take risks with kids in the car—it's safer to call a driver to take the car for repairs, and the insurance might even cover the towing fee.