What Causes the ABS Red Light to Illuminate?

[Ray]

ABS light illumination can occur in various states, each with different fault causes and corresponding solutions, as detailed below: State 1: ABS warning light remains constantly lit (most common). Cause 1: The ABS wheel speed sensor's sensing area is covered by contaminants such as mud or dirt, affecting its ability to detect vehicle speed signals. This prevents the ABS control module from determining vehicle speed or calculating wheel slip rates, thereby disabling its ability to issue appropriate commands for brake adjustment. Solution: Clean the dirt from the wheel speed sensor and adjust the gap between the sensor and the tone ring to restore normal function. Cause 2: Poor signal transmission due to loose system wiring connections or faulty ABS relay contacts. Solution: Inspect wiring connections and re-secure any loose connections. State 2: ABS warning light intermittently illuminates but turns off during acceleration. Cause: When multiple electrical components are in use, battery voltage drops below 10.5V. As engine speed increases, voltage rises and the ABS light extinguishes. This may also indicate insufficient power supply voltage to the ABS system due to poor terminal contact or grounding issues. Solution: Check battery specific gravity; inspect charging system; examine power supply components (e.g., voltage relay or poor power connections). State 3: ABS warning light remains illuminated after engine start until engine IFF (Ignition Off) occurs. Cause: Poor grounding connection of ABS hydraulic valve body; faulty wiring connections at ABS hydraulic valve body; ABS control module malfunction. Solution: Loosen and retighten hydraulic valve body ground screw, cleaning contact surfaces if necessary; check for enlarged connector gaps; replace ABS or ABS/ASR control module. State 4: ABS warning light illuminates during high-speed driving. Cause: ABS control module detects excessive speed difference between rear and front wheels; incorrect tire or wheel rim specifications. Solution: Verify proper tire and wheel rim specifications as indicated on vehicle specifications or fuel filler cap label. State 5: ABS warning light flashes intermittently. Cause: Improper brake light switch adjustment; internal contact failure in brake lights. Solution: With engine running, depress brake pedal and manually push brake switch linkage downward to its limit, then release pedal to complete self-calibration; replace brake light switch if necessary. When the ABS warning light is illuminated, continued driving is not recommended. An active ABS light indicates malfunction in the anti-lock braking system. During emergency braking, wheel lock-up may occur, potentially causing loss of vehicle control and skidding, preventing the driver from decelerating or adjusting vehicle trajectory - presenting significant safety risks.

[Colton]

A few days ago, the ABS light in my car suddenly turned on, which made me a bit nervous. Later, I asked a car-savvy friend to take a look together. He explained that it might be an issue with the wheel speed sensor, commonly caused by mud buildup from off-road driving, sensor damage, or loose wiring affecting signal transmission. If the ABS system fails, the wheels may lock up during hard braking, significantly increasing skidding distance and accident risk. Other possibilities include control unit software issues, blown fuses, or low brake fluid levels. For self-inspection, you can clean the sensor area around the wheels, but it's best not to delay—visit a professional repair shop as soon as possible to read the error codes with diagnostic tools. Safety comes first; don’t wait until an accident happens to address it. I’ve had a similar experience myself, and delaying repairs can lead to brake failure.