Steering: Description and Operation

DESCRIPTION
The variable assist power steering system consists of the following components:
^ Vehicle dynamics control module.
^ Power rack and pinion steering gear.
^ Power steering auxiliary actuator.
^ Rotary valve assembly (part of power steering short rack).
^ Power steering left turn pressure hose.
^ Power steering return hose.
^ 10-micron in-line filter.
^ CIII power steering pump.
^ Power steering pump reservoir.
^ Oil cooler-to-reservoir hose.
^ Auxiliary combination power steering and transaxle oil cooler.
^ Power steering reservoir pump hose.
^ Necessary wires and connectors.

OPERATION
The variable assist power steering (VAPS) system operates as follows:
^ It uses a solenoid-powered power steering auxiliary actuator and a rotary valve in the steering gear with two independent hydraulic circuits called the primary and secondary circuits.
^ During parking and low speed operation, the flow from the power steering pump is routed to the primary circuit by an electrically controlled power steering auxiliary actuator.
^ As vehicle speed increases, the power steering auxiliary actuator valve gradually opens, allowing an increasing amount of fluid to the secondary circuit.
^ The power steering auxiliary actuator valve is a pressure-balanced variable orifice valve, controlled by a solenoid. In addition to controlling vehicle suspension, the vehicle dynamics control module receives inputs from a vehicle speed sensor (VSS) and signals the spool to adjust the opening of the power steering auxiliary actuator according to a look-up table in the vehicle dynamics control module.