What causes the ABS light to come on in a Volkswagen Bora?

[MacSimon]

ABS light can illuminate in various states, with different causes and solutions for each state, as detailed below: State 1: ABS warning light stays on (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 unit from determining the vehicle speed and 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 transmission due to loose system wiring connections or faulty ABS relay contacts, leading to system malfunction. Solution: Inspect wiring connections and reconnect any loose parts. State 2: ABS warning light intermittently illuminates but turns off during acceleration. Cause: When multiple electrical devices are in use, the battery voltage may drop below 10.5V. As engine speed increases and voltage rises, the ABS light turns off. This can also occur if the ABS system's power supply voltage is too low, such as 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 remains on after engine start and only turns off when the engine is turned off (IGFF). Cause: Poor grounding connection of the ABS hydraulic valve body; poor electrical connector contact on the ABS hydraulic valve body; ABS control unit failure. Solution: Loosen and then retighten the grounding screw of the hydraulic valve body, cleaning the contact surface if necessary; check if the connector gap has widened; replace the ABS or ABS/ASR control unit. State 4: ABS warning light illuminates during high-speed driving. Cause: At high speeds, the ABS control unit detects a significant discrepancy between rear and front wheel speed signals; incorrect tire or wheel rim specifications. Solution: Refer to the vehicle's specified tire and wheel rim sizes, 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: With the engine running, press the brake pedal, push the brake switch linkage down fully with your 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. 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, preventing the driver from slowing down or adjusting the vehicle's path, posing significant safety risks.

[McCamilla]

The ABS light came on in my Volkswagen Bora, which is quite common. ABS stands for Anti-lock Braking System, and when the light is on, it means there might be an issue with the braking system that shouldn't be ignored. The most common cause is a dirty or faulty wheel speed sensor—mud or dust blocking the sensor can interfere with the signal. Other possibilities include loose wiring, a blown fuse, or a faulty ABS module. The wheel sensors are positioned low, making them especially prone to getting dirty after driving through waterlogged roads. The check is simple: clean the sensor area near the wheels. If the light stays on, you'll need to visit a repair shop to read the fault codes with a diagnostic tool. Last time, I tried cleaning it myself, but the issue persisted, and I ended up having a professional technician replace the sensor. To prevent minor issues, try to avoid excessively dirty roads when driving and keep up with regular maintenance. Safety comes first—when the ABS light is on, the tires are more likely to skid during braking, which is especially dangerous at high speeds. It's best to pull over to a safe spot and address the issue.