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

[SabrinaDella]

There are various states of the ABS light being on, with different causes and solutions for each state, as detailed below: 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's speed and the wheel's 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: Poor signal due to loose connections between system lines or poor contact of the ABS relay, leading to system failure. Solution: Check the connection points of the lines and reconnect any loose parts. State 2: ABS warning light intermittently comes on but turns off when accelerating. Cause: When multiple vehicle electrical devices are in use, the battery voltage drops below 10.5V. The ABS indicator turns off as the engine speed increases and voltage rises. This may also occur if the ABS system's power supply voltage is too low due to poor terminal contact or grounding issues. Solution: Check the battery's specific gravity, inspect the charging system, and 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 contact of the ABS hydraulic valve body's wire connector; ABS computer malfunction. 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 if needed. 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. This may also occur due to 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 of the brake light. Solution: With the engine running, press the brake pedal and 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 if necessary. If the ABS warning light is on, it is advisable not to continue driving. An illuminated ABS light indicates a malfunction in the vehicle's anti-lock braking system. During emergency braking, if the wheels lock up, the vehicle may skid uncontrollably, making it difficult for the driver to slow down or adjust the vehicle's trajectory, posing significant safety risks.

[OFelix]

I've been driving for many years, and ABS stands for Anti-lock Braking System. When the light comes on, it's usually a system reminder or fault warning. During emergency braking, it prevents the wheels from completely locking up, allowing you to maintain steering control and avoid skidding or rollover. I remember once braking hard on a slippery highway when the ABS automatically activated, and the car stopped steadily without skidding; without it, I would have lost control. I always advise friends not to ignore the ABS light—if it comes on, take it to a repair shop to check for sensor, wiring, or brake fluid issues. Long-term neglect increases the risk of accidents, especially in rain or snow. Checking the braking system during regular maintenance can prevent trouble—driving safety is no small matter. Don't try to fix it yourself; professional diagnosis is the way to go.