Express 1/2 Ton Van V8-305 5.0L VIN M SFI (1998)
Steering Wheel Speed Sensor: Description and Operation
POWER STEERING HYDRAULIC SYSTEM
The Electronic Variable Orifice (EVO) power steering pump is a conventional power steering pump with a Steering Assist Control Solenoid mounted
to the outlet port. When driving conditions require less hydraulic fluid, a flow control valve restricts the flow of fluid.
STEERING ASSIST CONTROL SOLENOID
Steering Assist Control Solenoid Location
Electronic Variable Orifice (EVO) Actuator Assembly
The Steering Assist Control Solenoid, mounted on the power steering pump, contains a solenoid operated valve. Discharged fluid passes through an
orifice in the solenoid. As the vehicle speed increases, the EVO/Passlock Module increases the PWM signal to the Steering Assist Control Solenoid.
Higher current gradually moves the valve further and further into the orifice. This action restricts the passage of fluid flow through the orifice,
reducing power assist in the steering gear.
Because the EVO/Passlock Module sends a variable signal, the Steering Assist Control Solenoid provides variable levels of power assist. The EVO
system therefore consistently adjusts power steering assist for changing vehicle speeds and driving conditions.
ELECTRONIC VARIABLE ORIFICE (EVO)/PASSLOCK MODULE
