Steering: Description and Operation

NOTE: This vehicle is available either with standard power steering or with an optional speed-sensitive variable-assist power steering system.

The power steering system consists of these six major components. Power Steering Pump, Power Steering Gear, Power Steering Reservoir, Power Steering Supply and Pressure Hoses, and Power Steering Fluid Return Hose. Turning of the steering wheel is converted into linear travel through the meshing of the helical pinion teeth with the rack teeth. Power assist steering is provided by an open center, rotary type control valve. It is used to direct oil from the power steering pump to either side of the integral steering rack piston.

Available as an option on this vehicle, is a speed sensitive variable-assist power steering system. This system is an electronically controlled, variable-assist type of power steering system. Speed-proportional, variable-assist power steering provides additional assist while the vehicle is stationary and at slow driving speeds. This additional power steering assist reduces the steering effort required by the driver for slow speed driving and parking maneuvers. Speed proportional variable-assist power steering then provides less steering assist at highway speeds, to maintain the firm, responsive feel of the standard non speed-proportional variable-assist power steering system.

Road feel is controlled by the diameter of a torsion bar which initially steers the vehicle. As steering effort increases as in a turn, the torsion bar twists, causing relative rotary motion between the rotary valve body and valve spool. This movement directs oil behind the integral rack piston, which in turn, builds up hydraulic pressure and assists in the turning effort.

SPEED PROPORTIONAL STEERING CIRCUIT OPERATION
The speed proportional steering module is mounted on the rack and pinion assembly This module adjusts the amount of power steering assist the operator receives based on vehicle speed.

At slower vehicle speeds power steering assist is increased, and at higher vehicle speeds the assist is decreased. A solenoid control valve is mounted in the power steering line and uses a variable orifice to control the assist.

Power for the steering module is provided on the F20 circuit. This circuit is protected by a 10 amp fuse located in cavity 6 of the junction block. Feed for the fuse is supplied on the A22 circuit from the ignition switch. The fuse is HOT in the RUN position only

The A22 circuit is protected by a 40 amp fuse located in cavity J of the Power Distribution Center (PDC). Circuit A2 connects the PDC to the ignition switch.

Ground for the system is provided on the Z1 circuit and terminates at the left frame rail.

The steering module receives the vehicle speed input from the G7 circuit. Circuit G7 is an output from the Transmission Control Module (TCM).