What Causes the ABS Yellow Light to Stay On?

[LaLena]

ABS light can illuminate in various states, and different states have different causes and solutions. 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 mud, sludge, 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 wheel slip rate, thus failing to issue appropriate commands to adjust braking. Solution: Clean the dirt on 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 lines or poor contact in the ABS relay can cause signal issues, leading to system failure. Solution: Check the line 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. The ABS system power supply voltage is too low, possibly 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; poor contact in the ABS hydraulic valve body wiring connector; ABS computer malfunction. Solution: Loosen the grounding screw of the hydraulic valve body, then retighten it. Clean the contact surface if necessary. Check if the connector gap has widened. Replace the ABS or ABS/ASR computer if needed. 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. Incorrect tire or wheel rim specifications may also be a factor. 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: Start the engine, press the brake pedal, and use a finger to push the brake switch linkage down fully. 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 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.