What Causes the ABS Light to Frequently Illuminate?

[MacFinley]

ABS light illumination can occur in various states, each with different causes and solutions. Details are as follows: State 1: ABS warning light remains constantly on (most common). Cause 1: The ABS wheel 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 control unit from determining the vehicle speed and wheel slip rate, thus failing to issue appropriate commands to regulate braking. Solution: Clean the dirt from the wheel speed sensor and adjust the gap between the sensor and the signal ring to restore normal function. Cause 2: Loose connections between system wiring or poor contact of the ABS relay lead to signal issues, causing system failure. Solution: Inspect wiring connections and reconnect any loose parts. State 2: ABS warning light intermittently illuminates but turns off when accelerating. Cause: When multiple vehicle electrical devices are in use, the battery voltage drops below 10.5V. As engine speed increases, voltage rises, and the ABS light turns off. This may also occur due to insufficient power supply voltage to the ABS system, such as poor terminal contact or grounding issues. Solution: Check battery specific gravity; inspect the charging system; examine the power supply (e.g., voltage relay or poor power contact). State 3: ABS warning light remains 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 electrical connector contact of the ABS hydraulic valve body; ABS control unit failure. Solution: Loosen and retighten the grounding screw of the hydraulic valve body, cleaning the contact surface if necessary; check if connector gaps have widened; replace the ABS or ABS/ASR control unit. State 4: ABS warning light illuminates during high-speed driving. Cause: At high speeds, the ABS control unit detects a significant discrepancy between rear and front wheel speed signals; incorrect tire or wheel rim specifications. Solution: Refer to the vehicle's tire and wheel rim specifications, typically listed on the fuel tank cap sticker. State 5: ABS warning light intermittently illuminates. 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 manually push the brake switch linkage fully downward, then release the pedal to complete self-positioning; replace the brake light switch if necessary. If the ABS warning light is on, it is advisable to avoid continued driving. An illuminated ABS light indicates a malfunction in the anti-lock braking system. During emergency braking, wheel lock-up can cause the vehicle to skid uncontrollably, preventing the driver from slowing down or adjusting the vehicle's path, posing significant safety risks.