What Causes ABS Failure in Volkswagen Tiguan?

[StGraham]

There are various states of the ABS warning light being on, 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 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 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 failure. Solution: Check wiring connections and reconnect any loose parts. State 2: ABS warning light intermittently turns on but goes off when accelerating. 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. 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, charging system, and 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 wiring; loose wiring connectors in the ABS hydraulic valve body; ABS computer malfunction. Solution: Loosen and retighten the hydraulic valve body's grounding screw, cleaning the contact surface if necessary. Check for enlarged gaps in the connector and replace the ABS or ABS/ASR computer if needed. State 4: ABS warning light turns on during high-speed driving. Cause: The ABS computer detects a significant discrepancy between rear and front wheel speeds during high-speed driving; 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 turns on. Cause: Improper adjustment of the brake light switch; poor internal contact in the brake light. Solution: With the engine running, press the brake pedal and push the brake switch linkage down fully with your fingers. Release the brake pedal to complete self-positioning. 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 trajectory, posing significant safety risks.

[StLukas]

The ABS malfunction in the Volkswagen Tiguan is primarily attributed to issues with the wheel speed sensors. These sensors, located near the wheels, are prone to accumulating mud and snow debris during rainy or snowy conditions, leading to intermittent signals. The Tiguan's sensors are positioned relatively low, making them susceptible to dirt buildup. Additionally, aging wiring connectors can oxidize or loosen over time, resulting in poor contact, especially on bumpy roads. The control unit might also malfunction due to voltage fluctuations or moisture exposure, triggering errors. When the ABS fails, wheels may lock up during braking, posing a high risk of skidding or even rollovers, particularly on slippery surfaces. Owners are advised to drive cautiously if the ABS warning light illuminates and promptly visit a professional workshop for a diagnostic scan. Replacing a minor sensor or cleaning it can be cost-effective and enhance safety—avoid delaying repairs until an accident occurs.