What are the reasons for the ABS warning light to illuminate?
2 Answers
ABS warning light can illuminate in various states, and the causes and solutions differ depending on the state. The details are as follows: State 1: ABS warning light stays on (most common). Cause 1: The ABS wheel speed sensor's sensing part 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 speed and the wheel slip rate, thus failing to issue appropriate commands to regulate braking. Solution: Clean the contaminants 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 lead to signal issues, causing system failure. Solution: Check the 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 may drop below 10.5V. As the engine speed increases and the voltage rises, the ABS warning light turns off. Alternatively, the ABS system 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, and 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, loose wiring connections in the ABS hydraulic valve body, or ABS computer malfunction. Solution: Loosen and retighten the grounding screw of the hydraulic valve body, clean the contact surface if necessary, check for enlarged gaps in the connectors, or replace the ABS or ABS/ASR computer. State 4: ABS warning light illuminates during high-speed driving. Cause: During high-speed driving, 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. State 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, push the brake switch linkage down with a finger, release the brake pedal to complete the self-setting position, or replace the brake light switch. If the ABS warning light is on, it is recommended not to continue driving. An illuminated ABS light 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.
A few days ago, my ABS warning light suddenly came on, which really made me nervous. I quickly recalled possible causes: the wheel speed sensor might be dirty or damaged from impact—it specifically detects wheel speed; the ABS control module could be faulty, which is the core component managing the entire system; a fuse might have blown, protecting the circuit from excessive current; poor or short-circuited wiring connections, possibly due to aging or loosening; or it could be due to insufficient battery power, affecting the system's power supply. Last time I encountered this issue, it was because the sensor got clogged with mud after rain, and cleaning it fixed the problem. But without ABS, the wheels may lock up during emergency braking, which is quite dangerous. I recommend not delaying and getting it checked by a professional shop as soon as possible.
