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. There are several conditions under which the ABS light may illuminate, each with different causes and solutions: Condition 1: ABS warning light stays on continuously (most common). Cause 1: The ABS speed sensor's sensing area 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 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 speed sensor and the signal ring to restore normal function. Cause 2: Loose connections in the system wiring or poor contact in the ABS relay lead to signal issues, causing system failure. Solution: Check the wiring connections and reconnect any loose parts. Condition 2: ABS warning light intermittently illuminates but turns off during acceleration. Cause: When multiple vehicle electrical components are in use, the battery voltage may drop below 10.5V. As the engine speed increases, the voltage rises, and the ABS light turns off. 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). Condition 3: ABS warning light stays on after the engine starts 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 a faulty ABS computer. Solution: Loosen and retighten the grounding screws on the hydraulic valve body, clean the contact surfaces if necessary, check for enlarged gaps in the connectors, and replace the ABS or ABS/ASR computer if needed. Condition 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, or incorrect tire or wheel rim specifications. Solution: Refer to the vehicle's tire and wheel rim specifications, as indicated on the label near the fuel tank cap. Condition 5: ABS warning light intermittently illuminates. Cause: Improper adjustment of the brake light switch or poor internal contact in the brake light. Solution: Start the engine, press the brake pedal, manually push the brake switch linkage down completely, then release the brake pedal to reset the position. Replace the brake light switch if necessary.
