What Causes the Anti-Slip Light and ABS Light to Stay On?

[AthenaMarie]

ABS light can illuminate in various states, with different causes and solutions for each state, as detailed below: State 1: ABS warning light stays on (most common). Cause 1: The ABS wheel 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 control unit from determining the vehicle speed or the wheel slip rate, thus failing to issue appropriate commands to adjust 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 in the system wiring or poor contact in the ABS relay can cause signal issues, leading to system failure. Solution: Inspect the wiring connections and reconnect any loose parts. State 2: ABS warning light intermittently illuminates but turns off during acceleration. Cause: When multiple electrical components are in use, the battery voltage may drop below 10.5V. As the engine speed increases and voltage rises, the ABS warning 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 verify 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; loose wiring connections in the ABS hydraulic valve body; or a faulty ABS control unit. Solution: Loosen and retighten the grounding screw of the hydraulic valve body, cleaning the contact surface if necessary. Check for enlarged gaps in the connectors. Replace the ABS or ABS/ASR control unit if needed. State 4: ABS warning light illuminates during high-speed driving. Cause: At high speeds, the ABS control unit 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 tire and wheel rim specifications, as indicated on the fuel tank cap label. State 5: ABS warning light intermittently illuminates. Cause: Improper adjustment of the brake light switch; poor internal contact in the brake light. Solution: With the engine running, press the brake pedal and manually push the brake switch linkage down to its limit, then release the pedal to complete the self-setting process. Replace the brake light switch if necessary. If the ABS warning light is on, it is recommended not to continue driving. An illuminated ABS light indicates a fault in the anti-lock braking system. During emergency braking, locked wheels can cause the vehicle to skid uncontrollably, preventing the driver from slowing down or adjusting the vehicle's trajectory, posing significant safety risks.

[Arwen]

Last year, my car had an issue where both the traction control light and ABS light came on simultaneously, which really freaked me out. I immediately slowed down and pulled over to the side of the road. Later, at the repair shop, the technician said it was likely due to dirty or faulty wheel speed sensors—these components detect wheel rotation speed near the wheels. If the signal is inaccurate, the ABS (Anti-lock Braking System) and traction control systems malfunction, triggering the warning lights. Other possible causes include aging or loose wiring, a faulty ABS control module, or a blown fuse, which is also common. At the time, cleaning the sensors temporarily fixed the issue, but looking back, such problems shouldn’t be delayed, especially during rain or snow when skidding risks increase. Now, I regularly inspect the tires and brake areas to prevent dirt buildup. Safety first—when warning lights appear, it’s best to get a professional diagnosis ASAP to avoid accidents on the road.