Variable Assist Power Steering (VAPS)

The Variable Assist Power Steering (VAPS) system uses the existing steering components, a power steering auxiliary actuator and a power steering variable assist control to improve smoothness and handling characteristics.

The variable assist power steering system consists of the following components:
^ generic electronic module
^ power rack and pinion steering gear
^ power steering auxiliary actuator
^ rotary valve assembly (part of power steering short rack)
^ pressure and return hoses
^ high efficiency, power steering pump
^ power steering pump reservoir
^ power steering fluid cooler
^ necessary wires and connectors





The Variable Assist Power Steering (VAPS) system uses a rotary valve in the power rack and pinion 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 gradually opens, allowing an increasing amount of fluid to the secondary circuit. This secondary circuit requires more effort to reach a given level of assist.
^ The Generic Electronic Module (GEM) receives inputs from a Vehicle Speed Sensor (VSS) and provides the variable current to adjust the opening of the power steering auxiliary actuator valve.
^ The GEM is programmed to perform a self-diagnostic check every 16 milliseconds.
^ If a concern is detected, the GEM deactivates its output signals.
^ The GEM is programmed to perform an on-board diagnostic procedure when activated by the service technician.