Description & Operation

The Variable Effort Steering (VES) system, also referred to as an Electronic Variable Orifice (EVO) steering system, varies the effort required to turn the steering wheel based on vehicle speed. As vehicle speed increases, EVO system decreases the amount of pump fluid pressure applied to the steering gear. EVO system is controlled by Powertrain Control Module (PCM) located behind left end of instrument panel. PCM receives signals from Vehicle Speed Sensor (VSS) on transaxle. Based on VSS signals, PCM cycles EVO actuator on and off to control power steering pump pressure at the pump outlet hose fitting. See Figure .

When EVO actuator is off (de-energized), full pump pressure is allowed through pressure line outlet to steering gear. When EVO actuator is on (energized), pump fluid by-passes pressure line outlet and is routed back into pump, decreasing pump pressure to the steering gear. EVO actuator cycling occurs at vehicle speed of 12 MPH or greater. EVO system has self-diagnostic ability that is part of PCM self-diagnostics. See SELF-DIAGNOSTIC SYSTEM  under TESTING.