Circuit Description
The power steering pressure (PSP) switch is normally open to ground. Turning the steering wheel increases the power steering oil pressure. Increased power steering oil pressure puts an additional load on the engine that may be noticeable at idle. The PSP switch closes when the power steering system oil pressure is high enough to cause an undesirable idle condition. The powertrain control module (PCM) increases the throttle valve opening in order to maintain an acceptable idle quality and 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
Check for any of the following conditions:
| • | A PSP switch that does not close, or loss of ground at the PSP switch may cause the engine to stall when the power steering loads are high. |
| • | A PSP switch that does not open or a signal line shorted to ground may affect the idle quality. |
| • | Check for a malfunction in the IAC system if the PSP switch circuit is OK. Increase the engine idle speed using a scan tool to control the IAC valve. Diagnose an IAC system malfunction if the IAC valve does not respond to scan tool commands. |
An intermittent malfunction may be caused by a fault in the power steering pressure switch electrical circuit. Inspect the wiring harness and the components for any of the following conditions:
| • | Any backed-out terminals |
| • | Any improper mating of terminals |
| • | Any broken electrical connector locks |
| • | Any improperly formed or damaged terminals |
| • | Any faulty terminal-to-wire connections |
| • | Any physical damage to the wiring harness |
| • | A broken wire inside the insulation |
| • | Any corrosion of the electrical connections, the splices, or the terminals |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
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This step checks the PSP switch signal circuit for voltage from the PCM.
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This step checks the operation of the PSP switch.
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This step checks for a short to ground in the Diagnostic Request circuit. A short to ground in the Diagnostic Request circuit can cause the PCM to ignore the PSP switch input. A short in the Diagnostic Request circuit will cause the IAC duty cycle and the idle speed to remain fixed.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic System Check? | -- | |||
2 |
Did the scan tool indicate that the IAC Duty increased the specified amount when the steering wheel was turned all the way in either direction? | 4-7 % | The PSP switch is functioning normally | |
Is the voltage near the specified value? | B+ | |||
Does the test lamp illuminate when the steering wheel is turned to the right and to the left? | -- | |||
5 |
Was a repair necessary? | -- | ||
6 |
Was a repair necessary? | -- | ||
7 | Replace the PSP switch. Refer to PSP Switch Replacement . Is the action complete? | -- | -- | |
8 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | |
Was a repair necessary? | -- | Go to Diagnostic Aids | ||
10 | Operate the vehicle within the conditions under which the original symptom was noted. Does the system now operate properly? | -- | System OK | Go to Diagnostic Aids |
