Description & Operation
Electronically controlled, variable-assist, speed-proportional power steering, provides greater steering assist when stationary and at low speeds. As road speed increases, less power assist is provided to give firmer, more responsive feel.
Maximum assist is provided from zero to 25 MPH. Operational range of variable-assist, speed-proportional power steering is from about 25 to 60 MPH with minimum power available at about 60 MPH.
Variable assist is provided by controlling power steering fluid at power steering gear. Pressure is controlled by regulating fluid flow from steering gear back to power steering pump. A solenoid valve, located on the steering gear, controls power steering pressure by varying size of orifice which power steering fluid flows through back to pump.
The solenoid valve is controlled by steering gear mounted electronic Solenoid Control Module (SCM). The SCM receives vehicle speed signal from Transmission Control Module (TCM). On receiving vehicle speed signal, the SCM converts signal into an electrical current used by the solenoid control valve to vary orifice size. See Fig 1 .