What is the purpose of the eccentric shaft sensor?
2 Answers
In engines equipped with an electronic valve control system, the eccentric shaft sensor detects the position of the eccentric shaft. The eccentric shaft adjusts the camshaft to achieve optimal intake valve lift (which can be continuously adjusted) under all operating conditions. The eccentric shaft is adjusted by the electronic valve control servo motor. Here is an introduction to the eccentric shaft sensor: The eccentric shaft sensor is equipped with two independent angle sensors with opposite characteristics. The eccentric shaft sensor operates based on the magnetoresistive effect principle, where a ferromagnetic conductor changes its resistance under the influence of a magnetic field. The sensor features a redundant design structure, with two sensor elements housed in a single unit. One sensor serves as the primary unit, while its operation is monitored by a reference sensor.
The eccentric shaft sensor is primarily used to monitor a critical component of the engine's valve system. Take BMW's Valvetronic system as an example—this device is mounted on the side of the engine, specifically tracking the rotation angle of the eccentric shaft. The eccentric shaft controls valve lift, while the sensor acts like a 24/7 sentry, transmitting the shaft's real-time position to the engine control unit (ECU). Based on this data, the ECU adjusts valve opening, ensuring the engine maintains optimal breathing rhythm across different RPMs. Without it, the car may feel breathless during acceleration, and fuel consumption could spike. Though small, this sensor directly impacts driving smoothness and throttle response. It usually goes unnoticed during normal driving, but if it fails, the engine warning light will immediately alert you.
