What does the ABS warning light in a car mean?

[DelIsabela]

When the ABS warning light appears on your car's dashboard, it indicates a malfunction in the Anti-lock Braking System. If the wheels lock during emergency braking, the vehicle may skid uncontrollably, making it difficult for the driver to slow down or adjust the vehicle's trajectory, posing significant safety risks. The ABS light can illuminate in various states, each with different causes and solutions: State 1: ABS light stays on constantly (most common). Cause 1: The ABS speed sensor's sensing area is covered by dirt, mud, or other contaminants, affecting its ability to detect speed signals. This prevents the ABS computer from determining the vehicle's speed or wheel slip rate, thus failing to issue appropriate braking commands. Solution: Clean the contaminants from the speed sensor and adjust the gap between the sensor and the signal ring to restore normal function. Cause 2: Loose connections in the system wiring or poor contact in the ABS relay leads to signal issues. Solution: Check all wiring connections and re-secure any loose connections. State 2: ABS warning light intermittently illuminates, turning off during acceleration. Cause: When multiple electrical components are in use, battery voltage may drop below 10.5V. The light turns off as engine speed increases and voltage rises. This may also indicate insufficient power supply to the ABS system due to poor connections. Solution: Check battery specific gravity; inspect the charging system; examine power supply connections (including voltage relay or poor power contacts). State 3: ABS warning light remains on after engine start, only turning off when engine is shut down (IGFF). Cause: Poor grounding connection of ABS hydraulic valve body; faulty wiring connections at the hydraulic valve body; ABS computer malfunction. Solution: Loosen and retighten the hydraulic valve body ground screw, cleaning contact surfaces if necessary; check for enlarged connector gaps; replace ABS or ABS/ASR computer if needed. State 4: ABS warning light illuminates during high-speed driving. Cause: ABS computer detects significant speed difference between front and rear wheels; incorrect tire or wheel rim specifications. Solution: Verify correct tire and wheel rim specifications according to vehicle requirements (refer to label near fuel filler cap). State 5: ABS warning light intermittently flashes. Cause: Improperly adjusted brake light switch; internal contact issues in brake lights. Solution: With engine running, press brake pedal fully while manually pushing the brake switch lever downward, then release pedal to reset position; replace brake light switch if necessary.