What causes the ABS yellow light to come on?

[ColinLee]

ABS light can illuminate in various states, 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 wheel speed sensor's sensing area is covered by mud, sludge, or other contaminants, affecting its ability to detect the corresponding speed signal. This prevents the ABS computer from determining the vehicle speed or the wheel slip rate, thus failing to issue appropriate commands to regulate 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: Poor signal due to loose system wiring connections or poor contact in the ABS relay, leading to system malfunction. Solution: Check 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 engine speed increases, the voltage rises, and the ABS 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 valve body, or ABS computer malfunction. Solution: Loosen and retighten the hydraulic valve body's grounding screw, clean the contact surface if necessary, check for enlarged terminal gaps, and 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, typically found 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: With the engine running, press the brake pedal and manually push the brake switch lever down fully, then release the pedal to reset its position. Replace the brake light switch if necessary. If the ABS warning light is on, it is not recommended to continue driving. An illuminated ABS light indicates a malfunction in the anti-lock braking system. During emergency braking, locked wheels may cause the vehicle to skid uncontrollably, preventing the driver from slowing down or adjusting the vehicle's trajectory, posing significant safety risks.

[Kayla]

Previously, my ABS light came on because the sensor on the right front wheel was covered in mud, and it was resolved after cleaning at the repair shop. The ABS system monitors tire rotation speed through wheel speed sensors. If a sensor is too dirty or damaged, the computer will trigger a warning light when it fails to receive a signal. Aging or cracked wiring is also a common issue, especially for vehicles frequently driven on rough roads. Although less likely, a faulty ABS pump or control unit can also cause the light to illuminate. When the light is on, the brakes still function, but the wheels may lock up during hard braking, leading to skidding, which is more dangerous in rainy conditions. It's advisable to check the fault codes as soon as possible—typically, replacing a sensor wire costs just a few dozen dollars. If left unrepaired for a long time, the braking distance in emergencies may increase.

[JoshuaFitz]

The ABS light on indicates that the anti-lock braking system may have failed, making the vehicle prone to skidding during emergency braking. Common causes include wheel speed sensors being blocked by mud or metal debris, which can often be resolved by cleaning with a high-pressure water jet. Worn or detached wiring is most common on bumpy roads, and water seepage can cause short circuits during the rainy season. I recommend restarting the vehicle first when the light comes on. If the light remains on, drive slowly to a repair shop on flat roads. Avoid emergency braking and slippery sections during the trip. During inspection, prioritize checking the sensors near all four tires, and note that uneven tire tread depth can also cause signal errors. Don't delay repairs, as the risks are greater when driving in snowy conditions.

[OGabriel]

My car's ABS light has come on twice: the first time was due to a loose sensor connector, which was fixed by plugging it in tightly; the second time was because a mouse chewed through the wiring. The ABS system primarily relies on wheel position sensors to function, and these sensors can fail to send signals if they're covered in dirt. Installing new tires with incorrect sizes can also trigger an alarm. It's generally safe to drive when the light is on, but you'll lose anti-lock braking functionality during emergency stops. I recommend first checking the dashboard warning light status—if the handbrake light is also on, it might indicate a power supply issue. For simple troubleshooting, you can remove the tire yourself to inspect whether the sensor wiring is broken. However, for complex electrical faults, it's best to visit a professional repair shop where they can use diagnostic tools to read the fault codes—problems can usually be pinpointed within half an hour.