For 1990-2009 cars
Engine Controls Component Views
Engine Data Sensors (1 of 2)
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice

### 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.

1. 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.

2. This step checks the PSP switch signal circuit for voltage from the PCM.

3. This step checks the operation of the PSP switch.

4. 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
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Install a scan tool.
2. Start the engine.
3. Run the engine until a normal operating temperature is reached.
4. Turn OFF all accessories.
5. Monitor the IAC Duty Cycle parameter on the scan tool.
6. Turn the steering wheel to the right and to the left.
7. Return the steering wheel to the center, straight ahead position.

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

Go to Step 3

3 |

1. Turn ON the ignition, with the engine OFF.
2. Disconnect the PSP switch electrical connector.
3. Measure the voltage from the PSP switch connector to ground on the harness side with a digital multimeter (DMM).

Is the voltage near the specified value?

B+

Go to Step 4

Go to Step 5

4 |

1. Connect a test lamp to B+.
2. Probe the PSP switch connector on the switch side with the test lamp.
3. Start the engine.
4. Observe the test lamp while turning the steering wheel to the right and to the left.

Does the test lamp illuminate when the steering wheel is turned to the right and to the left?

--

Go to Step 9

Go to Step 6

5 |

1. Check for an open or a short to ground in the PSP switch signal circuit between the PCM and the PSP switch.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 10

Go to Step 8

6 |

1. Check for a faulty ground connection at the power steering pump.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 10

Go to Step 7

7 | Replace the PSP switch. Refer to PSP Switch Replacement . Is the action complete? | -- | Go to Step 10 | --
8 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 10 | --
9 |

1. Check for a short to ground in the Diagnostic Request circuit from the PCM connector C3 to the TE1 terminal of the underhood diagnostic link connector.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 10

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