Power Steering Pressure Switch: Description and Operation

Fig. 21 Power Steering Pressure Switch:

PURPOSE
On all vehicles, a power steering pressure switch is used to improve the vehicle's idle quality.

OPERATION
The pressure switch improves vehicle idle quality, by maintaining required engine idle speed when necessary, due to increased pressure in the power steering system. This increased pressure will slow down the power steering pump which will decrease engine idle speed.

The pressure switch functions by signaling the powertrain 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 will be maintained. The maintained engine idle speed compensates for the additional load, thus maintaining the required engine idle speed and idle quality.

When power steering pump pressure exceeds 4137 kPa (600 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 pressure sensing switch is located on the power steering gear.