What Causes the ABS Yellow Light to Illuminate on a Car?
2 Answers
There are various states of the ABS light being on, with different causes and solutions for each state. The details are as follows: State 1: ABS warning light stays on (most common). Cause 1: The ABS 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 adjust braking. Solution: Clean the dirt from the speed sensor and adjust the gap between the speed sensor and the signal ring to restore normal function. Cause 2: Poor signal due to loose connections between system lines or poor contact of the ABS relay, leading to system failure. Solution: Check the line connections and reconnect any loose parts. State 2: ABS warning light intermittently illuminates but turns off during acceleration. 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; examine the power supply (e.g., voltage relay or poor power contact). State 3: ABS warning light stays on after engine start and turns off only when the engine is turned off (IGFF). Cause: Poor grounding contact of the ABS hydraulic valve body; poor contact of the ABS hydraulic valve body wiring connector; ABS computer malfunction. Solution: Loosen the grounding screw of the hydraulic valve body, then retighten it, cleaning the contact surface if necessary; check if the connector gap has widened; 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; 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 of the brake light. Solution: Start the engine, press the brake pedal, push the brake switch linkage down fully with a finger, then 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. The 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.
My car also had the ABS yellow light issue last year, and looking back, it really gave me a hard time. It happened during a long drive on a rainy day when suddenly the yellow indicator light on the dashboard started flashing. I consulted some experienced drivers, and they said it might be due to mud on the ABS sensor or uneven wheel rotation. Later, at the repair shop, it turned out the left front wheel sensor was dirty, and after cleaning, it worked fine again. Other possible causes could be poor wire connections or a blown fuse, which can trigger false alarms from the system. It’s good to pay attention to external conditions while driving and avoid going too fast on muddy roads to reduce such issues. If left unaddressed, ABS failure can make braking unstable, especially on slippery roads, which is quite dangerous. So, I recommend getting it checked as soon as you notice the problem.
