What causes the ABS light to come on after a vehicle inspection?

[LaJames]

ABS light can indicate various conditions, with different causes and solutions for each state as follows: Condition 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 wheel speed signals. This prevents the ABS control unit from determining vehicle speed or wheel slip rate, thus failing to issue proper braking commands. Solution: Clean the wheel speed sensor and adjust its gap with the tone ring to restore normal function. Cause 2: Loose wiring connections or poor contact in ABS relays causing signal issues. Solution: Inspect wiring connections and secure any loose connections. Condition 2: ABS warning light intermittently illuminates but turns off during acceleration. Cause: Battery voltage drops below 10.5V when multiple electrical components are in use. The light extinguishes when engine RPM increases voltage. Possible low voltage supply to ABS system due to poor connections. Solution: Check battery specific gravity, charging system, and power supply connections (voltage relay or power contacts). Condition 3: ABS warning light remains on after engine start until ignition is turned off. Cause: Poor grounding of ABS hydraulic valve body; faulty wiring connections; ABS control unit malfunction. Solution: Loosen and retighten hydraulic valve body ground screws, clean contact surfaces if necessary; inspect connector gaps; replace ABS or ABS/ASR control unit. Condition 4: ABS warning light activates during high-speed driving. Cause: ABS control unit detects significant speed difference between front and rear wheels; incorrect tire or wheel specifications. Solution: Verify proper tire and wheel specifications per vehicle requirements (refer to fuel filler door sticker). Condition 5: ABS warning light flashes intermittently. Cause: Improper brake light switch adjustment; internal contact issues in brake lights. Solution: With engine running, depress brake pedal and manually push switch lever downward, then release pedal for self-adjustment; replace brake light switch if needed. When the ABS warning light is illuminated, continued driving is not recommended. ABS malfunction means loss of anti-lock braking function - wheels may lock during emergency braking, causing loss of vehicle control and preventing proper deceleration or trajectory adjustment, posing significant safety risks.