Power Steering Pressure Switch: Description and Operation

Power Steering Pressure Switch:

PURPOSE
The Power Steering Pressure (PSP) switch sends an input signal to the Powertrain Control Module (PCM) when the power steering pressure rises above 400-600 psi. The PCM uses this signal to adjust idle speed to compensate for additional load on the engine.

OPERATION
The normally shut PSP switch receives a 5.0 volt reference signal from the PCM. With no power steering pressure applied the reference voltage is shunted to ground along the SIG RTN circuit. When the power steering is engaged the switch opens and the PSP circuit increases to 5.0 volts.

RELATED DIAGNOSTIC TROUBLE CODES

DTC 519 - PSP circuit open during the Key On Engine Off (KOEO) self-test.
DTC 521 - PSP circuit did not change states during the Key On Engine Running (KOER) self-test.

Note: Some vehicles are equipped with a PSP switch software strategy, but do not have hardware (a PSP switch) released for the engine/vehicle application. False PSP trouble codes will be generated during the KOEO and KOER self-tests for these vehicles.