Power Steering Pressure Switch: Description and Operation

POWER STEERING PRESSURE SWITCH - PCM INPUT
A power steering pressure switch is used to improve the vehicle's idle quality. The pressure switch improves vehicle idle quality by causing a readjustment of the engine idle speed, as necessary, when increased fluid pressure is sensed in the power steering system.

The pressure switch functions by signaling the Powertrain Control Module that an increase in pressure of the power steering system is putting additional load on the engine. This type of condition exists when the front tires of the vehicle are turned while the vehicle is stationary and the engine is at idle speed. These periods of high pump load and low engine rpm are most commonly found during parking maneuvers. When the Powertrain Control Module receives the signal from the power steering pressure switch, it directs the engine to increase its idle speed. This increase in engine idle speed compensates for the additional load, thus maintaining the required engine idle speed and idle quality.

Power Steering Pressure Switch:

The power steering pressure switch is located on the power steering gear.

The switch provides an input to the PCM during
When power steering pump pressure exceeds 2758 kPa (400 psi), the switch is open. The PCM increases idle air flow through the IAC motor to prevent engine stalling. The PCM sends 12 volts through a resister to the sensor circuit to ground. When pump pressure is low, the switch is closed.