The electronic variable orifice (EVO) system increases
or decreases the amount of fluid leaving the power steering pump. This provides
the driver with a comfortable balance of steering wheel feel and power assist.
At vehicle standstill or at 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 an improved road feel and a greater directional stability
at highway speeds.
A sensor mounted on the steering column detects the steering wheel movements
associated with defensive driving maneuvers. A control module uses this sensor
input and the vehicle speed in order to adjust the amount of current to
the solenoid.
The EVO system consists of the following components:
• | The power steering (PS) solenoid actuator is located on the power
steering pump discharged fitting. |
• | The EVO/Passlockā¢ module is mounted on the instrument panel
carrier, beneath the radio. |
• | The steering handwheel speed sensor (HWSS) is located in the lower
bearing of the steering column. |
• | The vehicle speed sensor is located on the transmission output
shaft or on selectable four wheel drive the transfer case output shaft. |
• | The powertrain control module (PCM) is located in the engine compartment
on the left inner wheel well panel (diesel engines only). |
• | The vehicle control module (VCM) is located in the engine compartment
on the left inner wheel well panel (gasoline engines only). |