Power Steering Pressure Switch: Testing and Inspection

Diagnostic Chart:

Schematic:

CIRCUIT DESCRIPTION
The Power Steering Pressure (PSP) switch is normally open to ground. Turning the steering wheel increases power steering oil pressure. Increased oil pressure in the power steering system puts an additional load on the engine that may be noticeable at idle. The PSP switch will close before the load on the engine causes an idle condition which is undesirable. The Powertrain Control Module (PCM) increases the throttle-valve opening in order to maintain acceptable idle quality and in order to prevent an engine stall.

The voltage signal from the PSP switch to the PCM indicates less than one volt when the PSP switch is closed. The voltage signal is near battery voltage when the PSP switch is open.

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

A PSP switch that does not open a signal line that is shorted to ground may affect idle quality.

A fault in the electrical circuit of the power steering pressure switch may cause an intermittent malfunction. Inspect the wiring harness and the components for any of the following conditions:
^ Backed out terminals
^ Incorrect mating of terminals
^ Broken electrical connector locks
^ Incorrectly formed terminals or damaged terminals
^ Faulty terminal-to-wire connections
^ Physical damage to the wiring harness
^ A broken wire inside the insulation
^ Corrosion of electrical connections, of splices, or of terminals

TEST DESCRIPTION
The numbers below refer to the step numbers in the diagnostic table.
1. The Powertrain OBD System Check prompts the technician to complete some basic checks, and to store the applicable freeze frame data on the scan tool. This creates an electronic copy of the data that was taken when the fault occurred. The scan tool stores the information for later reference.
3. This step checks for voltage from the PCM, for an open, or for a short to ground in the PSP switch signal circuit.
4. This step checks for a poor ground connection at the power steering pump or for a faulty PSP switch.