RAM 3500 Truck 2WD V8-5.7L VIN D (2003)
Power Steering Pressure Switch: Description and Operation
DESCRIPTION
Fig. 9
A pressure sensing switch is used in the power steering system. It is mounted on the high-pressure steering hose. This switch will be used with both
3.7L, 4.7L and 5.7L engines. There is no pressure switch used for the 5.9L pump.
OPERATION
The switch is used on the 3.7L V-6, 4.7L & 5.7L V-8 engines.
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 re-close and engine idle speed will return to its previous
setting.
