What does it mean when the ABS indicator light on the dashboard is on?

[DelMolly]

When a car displays the ABS light, 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, making it difficult for the driver to slow down or adjust the vehicle's trajectory, posing significant safety risks. There are several scenarios where the ABS light may illuminate, each with different causes and solutions: Scenario 1: ABS warning 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 the corresponding speed signal. This prevents the ABS computer from determining the vehicle's speed and wheel slip rate, thus failing to issue appropriate commands to regulate braking. Solution: Clean the dirt 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 can lead to signal issues and system failure. Solution: Inspect the wiring connections and re-secure any loose connections. Scenario 2: ABS warning light intermittently illuminates and turns off when accelerating. Cause: When multiple vehicle electrical components are in use, the battery voltage may drop below 10.5V. As the engine speed increases and voltage rises, the ABS light turns off. This can 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). Scenario 3: ABS warning light remains on after engine start and only turns off when the engine is turned off (IGFF). Cause: Poor grounding contact in the ABS hydraulic valve body; loose wiring connections in the ABS hydraulic valve body; or ABS computer malfunction. Solution: Loosen and then re-tighten the grounding screw on the hydraulic valve body, cleaning the contact surface if necessary. Check for enlarged gaps in the connectors and replace the ABS or ABS/ASR computer if needed. Scenario 4: ABS warning light illuminates during high-speed driving. Cause: At high speeds, 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 recommended tire and wheel rim specifications, typically found on the sticker near the fuel tank cap. Scenario 5: ABS warning light intermittently illuminates. Cause: Improper adjustment of the brake light switch; internal poor contact in the brake light. Solution: With the engine running, press the brake pedal and use a finger to push the brake switch linkage fully downward. Release the brake pedal to complete the self-setting position. Replace the brake light switch if necessary.