ABS Operation and Fault Detection
Anti-lock Braking System (ABS) prevents wheel lockup during emergency stops by modulating brake pressure to individual wheels. Locked wheels lose steering control and create flat-spotted tires. ABS allows the driver to maintain steering while braking at maximum force. How ABS works: wheel speed sensors on each monitored wheel transmit continuous speed data to the ABS Electronic Control Unit (ECU). During a stop, if any wheel decelerates faster than the others (indicating impending lockup), the ECU rapidly cycles the brake pressure for that wheel: releases pressure (wheel regains some rotation), reapplies pressure, releases again — this cycling (typically 8-15 times per second) keeps the wheel at the threshold of lockup, maintaining both maximum braking force and tire contact with the road. Driver technique with ABS: apply firm, continuous braking pressure during emergency stops — do not pump the brakes (ABS does the pumping). Maintain steering inputs. ABS fault detection: the ABS warning light is yellow/amber and illuminates at startup for a self-check, then turns off within 3 seconds if the system passes. If the light remains on after startup, a fault is detected. If the light activates during driving, a fault has occurred. Faults are typically wheel speed sensor failures (most common), ECU failures, or wiring issues. A vehicle with an ABS fault can still be driven and braked normally — ABS falls back to standard braking, but without the anti-lock modulation. The fault should be repaired promptly.