SW L4-1.9L DOHC VIN 7 (1993)
Power Steering Pressure Control Valve: Description and Operation
EVO Solenoid Replacement.
Electrical Variable Orifice Valve Wiring.
DESCRIPTION
The optional power steering system used on Saturn is a rack and pinion design. The pump in this system features an Electrical Variable Orifice
(EVO) design. The major computer components of the power steering system are the EVO actuator, Vehicle Speed Sensor (VSS), and power
steering pressure switch.
NOTE: A Handwheel sensor is used on the Coupe model.
PURPOSE
Unlike conventional power assisted steering systems, the Electrical Variable Orifice (EVO) feature adjusts the amount of steering assist to the
speed of the vehicle. Reducing the amount of power steering assist, when not needed, reduces engine load thus improving fuel economy and
engine power at higher speeds. At higher vehicle speeds there is less of a need for steering assist. Higher assist is provided at low speeds and less
assist is provided at high speeds. The Powertrain Control Module (PCM) monitors and controls the sensors and actuators.
CIRCUIT OPERATION
The PCM will supply battery voltage and a ground for the Electrical Variable Orifice (EVO) solenoid. The PCM controls both the high side
(voltage input) and low side (ground control) to the solenoid so that current control is retained in the presence of any output fault condition.
