Variable Efforts Steering Description

Variable Effort Steering System Description and Operation
The Variable Effort Steering (VES) system controls the amount of steering effort needed to steer the vehicle as vehicle speed, or steering wheel position sensor input changes. The Electronic Brake Control Module (EBCM) controls an Electronic Variable Orifice (EVO) actuator located in the power steering pump's output fluid orifice. The actuator consists of an electromagnetic coil and a pintle valve which moves in and out of an orifice regulating power steering fluid flow. The EBCM commands current to the actuator from 0-619 ma. At low speeds, no current is commanded to the actuator and the pintle valve is fully retracted, which provides maximum fluid flow and full assist for easy turning and parking maneuvers. At higher speeds, more current is commanded to the actuator causing the pintle valve to move closer to the orifice which decreases fluid flow providing firmer steering (road feel) and directional stability. The VES system uses the steering wheel position sensor input to sense abrupt driving maneuvers. When the EBCM detects an abrupt maneuver, less current is commanded to the actuator to provide full steering assist. The VES system also uses the two rear Antilock Brake System (ABS) wheel speed sensor inputs to determine vehicle speed.