Steering: Description and Operation

Steering System
The power steering system consists of:
^ Power steering pump.
^ Fluid reservoir.
^ Rack and pinion steering gear.
^ Fluid cooler.
^ High and low pressure steering lines/hoses.
^ Variable assist power steering (VAPS) actuator.
^ Variable assist power steering (VAPS) module.

Principles of Operation
Variable Assist Power Steering (VAPS) The variable assist power steering (VAPS) system controls the level of power assistance available to the driver based on vehicle speed. Full power steering assist is provided to lessen steering effort and increase maneuverability. Steering assist will decrease gradually at a calibrated rate to raise steering effort for increased directional stability and greater road feel.

The VAPS module outputs a Pulse-Width-Modulated (PWM) current to the control valve actuator. The control valve actuator controls the hydraulic valve, which determines the amount of hydraulic assist provided to the steering gear. Based on vehicle speed, the amount of assistance provided varies with the control valve actuator current.

The vehicle speed is provided to the VAPS module by the powertrain control module (PCM).