This crankshaft speed sensor monitors engine rotation and sends a signal to the engine control unit for timing and diagnostic functions. It is mounted near the crankshaft tone ring and detects the passage of each tooth, providing the ECU with real-time crankshaft position and speed data. A failing sensor typically causes a no-start condition, erratic idle, or a check-engine light with a crankshaft position circuit fault. As an original-manufacturer component, the sensor body and internal magnet are matched to the original air gap specification, so no shimming or bracket adjustment is required during replacement.