What does it mean when the ABS light is on on the car dashboard?
2 Answers
There are multiple states of the ABS light being on, with different causes and solutions for each state. The details are as follows: State 1: ABS warning light stays on (most common). Cause 1: The ABS speed sensor's sensing part is covered by dirt, mud, or other contaminants, affecting the sensor's ability to detect the corresponding speed signal. This prevents the ABS computer from determining the vehicle speed and the wheel slip rate, thus failing to issue appropriate commands to adjust braking. Solution: Clean the dirt from the speed sensor and adjust the gap between the speed sensor and the signal ring to restore normal function. Cause 2: Loose connections between system lines or poor contact of the ABS relay result in poor signal quality, causing system failure. Solution: Check the line connections and reconnect any loose parts. State 2: ABS warning light intermittently turns on but goes off when accelerating. Cause: When multiple vehicle electrical devices are in use, the battery voltage drops below 10.5V. As the engine speed increases, the voltage rises, and the ABS light turns off. The ABS system power supply voltage is too low, possibly due to poor terminal contact or grounding issues. Solution: Check the battery's specific gravity; inspect the charging system; examine the power supply (e.g., voltage relay or poor power contact). State 3: ABS warning light stays on after engine start and only turns off when the engine is turned off (IGFF). Cause: Poor grounding contact of the ABS hydraulic valve body; poor electrical connection of the ABS hydraulic valve body; ABS computer failure. Solution: Loosen and then retighten the grounding screw of the hydraulic valve body, cleaning the contact surface if necessary; check if the connector gap has widened; replace the ABS or ABS/ASR computer. State 4: ABS warning light turns on during high-speed driving. Cause: At high speeds, the ABS computer detects a significant difference between the rear and front wheel speed signals; incorrect tire or wheel rim specifications. Solution: Refer to the vehicle's tire and wheel rim specifications, as indicated on the label near the fuel tank cap. State 5: ABS warning light intermittently turns on. Cause: Improper adjustment of the brake light switch; poor internal contact of the brake light. Solution: Start the engine, press the brake pedal, push the brake switch linkage down with your finger, then release the brake pedal to complete the self-setting position; replace the brake light switch. If the ABS warning light is on, it is recommended not to continue driving. The ABS light indicates a fault in the vehicle's anti-lock braking system. During emergency braking, if the wheels lock up, the vehicle may skid uncontrollably, preventing the driver from slowing down or adjusting the vehicle's trajectory, posing significant safety risks.
My car's ABS light came on a while ago, which is the warning for the Anti-lock Braking System. It happened after driving on muddy roads in the rain. When I stopped to check, I found the left front wheel sensor was covered in mud. The mechanic said these sensors are super sensitive - they count every wheel rotation, and mud blockage can interrupt the signal. Common failure points besides dirty or damaged sensors include wiring wear and water intrusion in the control module. I once had a case where the ABS pump relay burned out, and replacing it fixed the problem. Never ignore it - without ABS, tires can lock up and skid during emergency braking, especially dangerous in rainy conditions. If you notice this issue, drive carefully and get it checked with professional diagnostic equipment as soon as possible.
