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

[OTaylor]

When the ABS light is displayed on a car, it indicates a malfunction in the vehicle's Anti-lock Braking System. During emergency braking, if the wheels lock up, the vehicle may lose control and skid, preventing the driver from slowing down or adjusting the vehicle's trajectory, which poses 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 continuously (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 regulate 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 transmission due to loose connections in the system wiring or poor contact in the ABS relay, leading to system failure. Solution: Check the wiring 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 indicator light turns off. The ABS system's 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 until the engine is turned off (IGFF). Cause: Poor grounding contact in the ABS hydraulic valve body; poor contact in the ABS hydraulic valve body's electrical connector; ABS computer malfunction. Solution: Loosen the grounding screw on 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 discrepancy 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 sticker 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: With the engine running, press the brake pedal and use a finger to push the brake switch linkage down to its limit, then release the brake pedal to complete the self-setting position; replace the brake light switch.

[DiEliana]

When the ABS light comes on, it means there's a malfunction in the vehicle's anti-lock braking system, and it can no longer function properly. I've experienced this before with my older car, and whenever the light came on, I'd get particularly worried because ABS prevents wheel lock-up during emergency braking, helping the car stop steadily—especially useful on wet or snowy roads. Common reasons for the light coming on include a dirty wheel speed sensor, loose wiring, or a blown fuse. Once, when my car's ABS light was on, I found that the front wheel sensor was dirty, and cleaning it restored normal function. However, if ignored, the brake pedal can become stiff during braking, making it easier to lose control, so it's important to drive carefully to a safe place for inspection immediately. First, check the corresponding fuse in the fuse box to see if it's blown and try replacing it; if that doesn't work, head to a repair shop as soon as possible—don't take risks. Regularly cleaning around the wheels can reduce such issues, and developing the habit of checking the dashboard while driving is also crucial. Spending a little time on maintenance can save a lot of hassle later.