Electronic Variable Orifice (EVO)

The Electronic Variable Orifice (EVO) system increases or decreases the amount of fluid leaving the power steering pump. This provides the driver with a comfort able balance of steering wheel feel and power assist.

At vehicle stand still or very low speeds, the system allows full hydraulic fluid flow for maximum power assist and reduced steering effort. As the vehicle gains speed, a variable orifice closes at the steering pump which reduces the pump fluid flow. This action provides a stiffer steering wheel response for improved road feel and greater directional stability at highway speeds.

A sensor mounted on the steering column, detects the rapid steering wheel movements associated with defensive driving maneuvers. A control module uses this sensor input and vehicle speed to adjust the amount of current to the fluid flow actuator.

The EVO System consists of the following components:
- The Power Steering Fluid Flow Actuator is located on the power steering pump discharge fitting.
- The Power Steering Control Module is mounted on the instrument panel carrier, to the right of the steering column.
- The [1][2]Steering Wheel Position Sensor is located in the lower bearing of the steering column.
- The Vehicle Speed Sensor is located on the transmission (two wheel drive) or transfer case (four wheel drive).
- The Vehicle Speed Sensor Buffer is located on the bottom of the Powertrain Control Module (PCM) tray (diesel engines only).
- The Vehicle Control Module (VCM) is located in the engine compartment on the left inner wheel well panel (gas engines only).