Steering: Description and Operation

The power steering system is a rack and pinion design, featuring an Electronic Variable Orifice (EVO) design pump.
Unlike conventional power steering systems, the EVO feature adjusts the amount of steering assist according to the speed of the vehicle, which is monitored by a vehicle speed sensor (VSS). This information is read electronically by the Powertrain Control Module (PCM), which commands the EVO actuator to control the power steering pump output flow.
At low speeds, where high levels of assist are desired, the EVO actuator is open further, providing more flow to the steering gear and greater assist. At higher speeds, the actuator is closed further, providing less pump flow and less steering assist and improved road feeling. All of the additional flow of the pump that is not needed by the gear is allowed to return to the reservoir through a bypass.