Steering: Description and Operation
Steering SystemThe power steering system consists of the following components:
^ Power steering pump
^ Power steering fluid reservoir
^ Steering gear
^ Power steering fluid cooler
^ Power steering lines
^ Steering column
^ Steering column shaft
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. Below 3.2 km/h (2 mph), full power steering assist is provided to lessen steering efforts and increase maneuverability. Between 3.2 km/h (2 mph) and 191 km/h (119 mph), steering assist decreases gradually at a calibrated rate to raise steering efforts for increased directional stability and greater road feel. Above 191 km/h (119 mph), steering assist is constant.
The VAPS module outputs a pulse-width-modulated (PWM) current to the control valve actuator. The control valve actuator controls the hydraulic valve that determines the amount of hydraulic assist provided to the steering gear. The amount of assistance provided varies with the control valve actuator current, which is based on vehicle speed.
The vehicle speed is provided to the VAPS module by the powertrain control module (PCM).
Power Steering
Power Steering - Hydraulic System
1. The power steering system consists of the:
^ power steering pump.
^ power steering fluid reservoir.
^ rack-and-pinion steering gear.
^ power steering fluid cooler.
^ power steering pressure and return lines/hoses.
^ variable assist power steering (VAPS) actuator.