Power Steering Pressure Switch: Description and Operation
SWITCH-POWER STEERING PRESSUREDESCRIPTION
A pressure sensing switch is used in the power steering system. It is mounted on the high-pressure steering hose. This switch will only be used on HD vehicles with the 5.7L engines. There is no pressure switch used for the 3.7L, 4.7L, 5.9L Diesel engine or the 5.7L LD vehicle pump.
OPERATION
The switch is used on the 5.7L V8 engines HD vehicles only.
The power steering pressure switch provides an input to the Powertrain Control Module (PCM). This input is provided during periods of high steering pump load and low engine rpm; such as during parking maneuvers. The PCM increases the idle speed through the Idle Air Control (IAC) motor. This is done to prevent the engine from stalling under the increased load.
When steering pump pressure exceeds 3275 kPa ± 690 kPa (475 psi ± 100 psi), the Normally Closed (NC) switch will open and the PCM will increase the engine idle speed. This will prevent the engine from stalling.
When pump pressure drops to approximately 1379 kPa (200 psi), the switch circuit will reclose and engine idle speed will return to its previous setting.