Chart C-1C Power Steering Pressure Switch Check

Diagnostic Chart:

Power Steering Pressure Switch Circuit:

CIRCUIT DESCRIPTION
The Power Steering Pressure (PSP) switch is normally open to ground, and the Engine Control Module (ECM) terminal will be near battery voltage.

Turning the steering wheel increases power steering oil pressure and its load on an idling engine. The pressure switch will close before the load can cause a poor idling condition.

Closing the switch causes the ECM voltage signal to read less than one volt. The ECM will increase the idle speed and prevent engine load stall.

CHART TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart.

1. Checks for ECM signal voltage and for an open, or a short to ground in BLU/WHT wire or for a faulty ECM.
2. Checks for a poor ground connection at the power steering pump and for a faulty PSP switch.

DIAGNOSTIC AIDS
A pressure switch that will not close, or loss of ground at the PSP switch may cause the engine to stop when power steering loads are high.

A switch that will not open or a signal line shorted to ground may affect idle quality.

An intermittent malfunction may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connections before component replacement.