What Causes the ABS Light to Illuminate on the Vehicle Dashboard?

[MacLena]

ABS light illumination can occur in various states, each with different causes and solutions, as detailed below: State 1: ABS warning light stays on continuously (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 and wheel slip rate, thus failing to issue appropriate commands to regulate braking. Solution: Clean the contaminants from the speed sensor and adjust the gap between the sensor and the signal ring to restore normal function. Cause 2: Poor signal transmission due to loose connections in the system wiring or poor contact in the ABS relay, leading to system malfunction. Solution: Inspect 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 drops below 10.5V. The ABS warning light turns off as the engine speed increases and voltage rises. 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). State 3: ABS warning light remains on after engine start and only turns off when the engine is turned off (IGFF). Cause: Poor grounding connection in the ABS hydraulic valve body; poor contact in the ABS hydraulic valve body wiring connector; ABS computer malfunction. Solution: Loosen and then retighten the grounding screw on the hydraulic valve body, cleaning the contact surface if necessary. Check for enlarged gaps in the connector; replace the ABS or ABS/ASR computer if needed. State 4: ABS warning light illuminates during high-speed driving. Cause: The ABS computer detects a significant discrepancy between rear and front wheel speed signals during high-speed driving. 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 label near the fuel tank cap. 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 use a finger to push the brake switch linkage fully downward. Release the brake pedal to complete the self-setting position. Replace the brake light switch if necessary. If the ABS warning light is on, it is advisable 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, preventing the driver from slowing down or adjusting the vehicle's trajectory, posing significant safety risks.

[LePaisley]

When the ABS light comes on, it's crucial to take it seriously. I believe this issue is mainly related to a malfunction in the anti-lock braking system. The most common problem is with the wheel speed sensors, especially when driving on muddy roads or during rainy weather. Dust and mud sticking to the sensor probes can disrupt the signal, causing the light to stay on. Additionally, the ABS control module might be faulty or experiencing software conflicts, which requires checking the error codes with a diagnostic computer. Another possible cause is a blown fuse, which occurs when the circuit is overloaded. Wiring harness issues, such as loose connections or aged and broken wires, can also trigger false alarms in the system. I once experienced this myself when my car, after seven or eight years of use, had worn wheel bearings that caused the sensor position to shift, leading to the light coming on. Safety is not something to take lightly—if the ABS light is on, the tires might lock up and skid during emergency braking, especially on wet or slippery roads, doubling the danger. It's best to take the car to a professional shop for inspection immediately and avoid attempting DIY repairs. Regularly cleaning around the wheel hubs during car washes can help prevent dust buildup.