When the car displays an 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 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, 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 its ability to detect the corresponding speed signal. This prevents the ABS computer from determining the vehicle's speed or the wheel's 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: Poor signal due to loose connections between system wires or poor contact in the ABS relay. Solution: Check the wire connections and reconnect any loose parts. State 2: ABS warning light intermittently turns on but goes off when accelerating. Cause: When multiple vehicle electrical devices are in use, the battery voltage may drop below 10.5V. As the engine speed increases, the voltage rises, causing the ABS indicator to turn off. Alternatively, the ABS system's power supply voltage may be too low 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 and only turns off when 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 wire 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 turns on during high-speed driving. Cause: At high speeds, 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, typically found on the label near the fuel tank cap. State 5: ABS warning light intermittently turns on. Cause: Improper adjustment of the brake light switch; poor internal contact in the brake light. Solution: Start the engine, press the brake pedal, push the brake switch linkage down with your finger, then release the brake pedal to complete the self-setting position; replace the brake light switch if necessary.
