Steering Gear: Description and Operation

DESCRIPTION
Available on certain models of this vehicle is an electronically controlled, speed-sensitive, variable-effort rack and pinion power steering system, better known as speed-proportional power steering.






The speed proportional power steering gear mounts in the same location as the standard power steering gear. It is mounted on the crossmember behind the engine. Externally, the main difference between a speed proportional power steering gear and a standard power steering gear is the presence of a solenoid control valve on the gear housing.

OPERATION
The speed-proportional power steering system reduces the steering effort required by the driver for low speed driving and parking maneuvers. Also, at higher speeds, more steering effort is required providing a more firm, responsive feel to the power steering system.
With the engine running and the vehicle speed between 0 kph (0 mph) and approximately 32 kph (20 mph), minimum steering effort is required. Between approximately 32 kph (20 mph) and 100 kph (60 mph), power steering effort will gradually increase based upon vehicle speed. Above approximately 100 kph (60 mph), maximum steering effort is required by the speed proportional steering system.
Variable-effort power steering is provided by controlling power steering fluid pressure at the power steering gear. A solenoid control valve located on the steering gear is used to control power steering gear return fluid pressure. The pressure is controlled by varying the size of an orifice.
The variable-assist speed-proportional solenoid control valve is controlled by the Body Control Module (BCM). The BCM receives the vehicle speed signal sent from the Powertrain Control Module (PCM). Upon receiving the vehicle speed signal from the PCM, the BCM converts that speed signal into an electrical current usable by the solenoid control valve for controlling the variable effort of the power steering system.