Power Steering Pressure Switch (4.7L)
A pressure sensing switch is included in the power steering system (mounted on the high-pressure line). See Fig 1 . The power steering pressure switch provides an input to the Powertrain Control Module (PCM). This input is provided during periods of high pump load and low engine RPM such as during parking maneuvers. The PCM will then increase 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 375-575 psi (2585-3965 kPa), 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 200 psi (1379 kPa), the switch circuit will re-close and engine idle speed will return to its previous setting.