Power Steering Pressure Switch: Description and Operation

Fig. 15 Power Steering Pressure Switch:

PURPOSE
On vehicles equipped with power steering, a power steering pressure switch is used to improve the vehicle's idle quality. The pressure switch improves vehicle idle quality, by controlling engine idle speed when required.

The switch (Fig. 15) provides an input to the PCM during periods of high pump load and low engine RPM; such as during parking maneuvers.

OPERATION
The pressure switch functions by signaling the power train control module, that the power steering system is putting additional load on the engine. This type of condition exists when turning the front tires of the vehicle, when the vehicle is stationary and the engine is at idle speed. When this condition is sensed by the power train control module, through a signal from the power steering pressure switch, engine idle speed is increased. This increase in engine idle speed compensates for the additional load, thus maintaining the require engine idle speed and idle quality.

When power steering pump pressure exceeds 2,758 kPa (400 psi), the switch is open. The PCM increases idle air flow through the IAC motor to prevent engine stalling.

When pump pressure is low, the switch is closed.

The power steering pressure switch is mounted directly to the power steering gear on vehicles requiring its usage.