What does it mean when the ABS light comes on in a Jetta?

[Camargo]

There are multiple scenarios for the ABS light being illuminated, each with different causes and solutions, as detailed below: Scenario 1: ABS warning light stays on constantly (most common). Cause 1: The ABS wheel speed sensor's sensing area is covered by dirt, mud, or other contaminants, affecting its ability to detect the corresponding speed signal. This prevents the ABS control module from determining the vehicle speed and wheel slip rate, thus failing to issue appropriate commands to regulate braking. Solution: Clean the debris 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 wiring connections or faulty ABS relay contacts. Solution: Inspect wiring connections and reconnect any loose terminals. Scenario 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. The light extinguishes as engine speed increases and voltage rises. Possible causes include insufficient ABS system supply voltage due to poor terminal contact or grounding issues. Solution: Check battery specific gravity; inspect charging system; verify power supply (e.g., voltage relay or poor power contact). Scenario 3: ABS warning light remains on after engine start until engine is turned off (IGFF). Cause: Poor grounding connection of ABS hydraulic valve body; faulty wiring harness connector of 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. Scenario 4: ABS warning light activates during high-speed driving. Cause: ABS control module detects significant discrepancy between rear and front wheel speeds during high-speed operation; incorrect tire or wheel rim specifications. Solution: Refer to vehicle's recommended tire and wheel rim specifications (typically listed on fuel filler cap sticker). Scenario 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 fully, then release pedal to complete self-calibration; replace brake light switch if necessary. When the ABS warning light is illuminated, it's advised to avoid continued driving as it indicates a malfunction in the anti-lock braking system. During emergency braking, locked wheels may cause loss of vehicle control and skidding, preventing the driver from decelerating or adjusting trajectory, posing significant safety risks.