What does it mean when the ABS light comes on in a car?

[Layla]

When a car displays the ABS light, it indicates a malfunction in the vehicle's Anti-lock Braking System. If the wheels lock up during emergency braking, the vehicle may lose control and skid, making it difficult for the driver to slow down or adjust the vehicle's trajectory, posing significant safety risks. There are several states in which the ABS light may illuminate, each with different causes and solutions, as detailed below: State 1: ABS warning light stays on constantly (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's speed and the wheel's slip rate, thus failing to issue appropriate commands to adjust braking. Solution: Clean the dirt off the speed sensor and adjust the gap between the speed sensor and the signal ring to restore normal function. Cause 2: Poor signal due to loose connections between system wires or poor contact in the ABS relay, leading to system failure. Solution: Check the wire connections and reconnect any loose parts. State 2: ABS warning light intermittently comes on and turns 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's power supply voltage is too low, possibly due to poor wire 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. Cause: Poor grounding contact in the ABS hydraulic valve body; poor contact in the ABS hydraulic valve body wire connector; ABS computer malfunction. Solution: Loosen the grounding screw of the hydraulic valve body, then retighten it, 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 comes on during high-speed driving. Cause: During high-speed driving, 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 comes on. Cause: Improper adjustment of the brake light switch; poor internal contact in the brake light. Solution: Start the engine, press the brake pedal, use a finger to push the brake switch linkage all the way down, then release the brake pedal to complete the self-setting position; replace the brake light switch.

[OJaxon]

I've personally witnessed the ABS light illuminating, which indicates the anti-lock braking system has detected a fault. The primary function of ABS is to prevent wheel lock-up during hard braking, helping the vehicle maintain directional control and avoid skidding. The causes can vary widely - from wheel speed sensors being covered in mud causing signal errors, to loose or corroded electrical connections, control unit software glitches, or even unstable battery voltage. When this light comes on, the basic braking function still works but you lose the anti-lock feature, significantly increasing risks on slippery roads or during emergencies as it may extend stopping distances and potentially cause accidents. My advice is don't delay - immediately use an OBD scanner to retrieve trouble codes and identify the issue, then visit a reputable repair shop. During routine maintenance, regularly clean the sensor areas to prevent dust buildup that could trigger faults. This proactive approach helps eliminate hazards promptly, putting driving safety first.