Description & Operation

Variable Effort Steering (VES) system varies the effort required to rotate the steering wheel by varying the power steering fluid flow rate in accordance with the vehicle speed. As vehicle speed increases, power steering pump fluid flow rate is decreased which provides the driver with firmer steering (road) feel and directional stability at high speeds. VES system consists of a Power Steering Control Module (PSCM), power steering solenoid actuator, steering wheel speed sensor and connecting hydraulic lines and electrical wiring.

The PSCM process vehicle speed information from Powertrain Control Module (PCM) and input signal from steering wheel speed sensor. The steering wheel speed sensor determines steering wheel rotating speed and delivers input signal to allow for full power steering assist during a quick maneuver. The PSCM then delivers a Pulse Width Modulated (PMW) output signal to power steering pump actuator. The power steering pump actuator uses the PMW signal from PSCM and moves a pintle into the orifice in the power steering pump to regulate fluid flow rate from power steering pump. A check valve is located on the inlet hose at steering gear assembly. Check valve reduces the amount of steering wheel movement when driving over rough surfaces while operating at speeds with reduced fluid flow rate from power steering pump.