For 1990-2009 cars
A/C Controls and Idle-Up Signals
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The power steering pressure (PSP) switch is a normally open switch. When the steering wheel is turned, causing power steering pressure to increase, the PSP switch closes and pulls the switch voltage to ground. The PCM increases the idle speed in order to prevent diminished engine idle quality or engine stalling, in response to a low PSP switch signal.

### Diagnostic Aids

Check for any of the following conditions:

• | A PSP switch that is shorted can cause the engine idle speed to remain high even when driving straight ahead.

• | A PSP switch that is incorrectly calibrated can cause the engine idle speed to remain low when the steering pump hydraulic pressure is high.

• | A faulty ground in the PSP switch can cause erratic switch operation. Inspect that the power steering (PS) pump and bracket are secure, ensuring a good path to ground. Inspect the PSP switch for a tight installation.

• | The power steering pump delivering low pressure

### 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 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 for voltage from the PCM or for an open or a short to ground in the PSP switch signal circuit.

3. This step checks for a inadequate ground connection at the power steering pump or a faulty PSP switch.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) 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 power steering pressure (PSP) switch on the scan tool.
6. Turn the steering wheel all the way to the right and all the way to the left.

Did the scan tool indicate ON when the steering wheel was turned all the way in either direction?

--

System OK

Go to Step 3

3 |

1. Turn ON the ignition, leaving 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 switch side of the PSP switch connector with the test lamp.
3. Start the engine.
4. Observe the test lamp while turning the steering wheel all the way to the right and all the way to the left.

Does the test lamp illuminated with the steering wheel turned all the way to the right or left?

--

Go to Diagnostic Aids

Go to Step 6

5 |

1. Check for an open or a short to ground in the PSP 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 9

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 9

Go to Step 7

7 | Replace the PSP switch. Refer to PSP Switch Replacement . Is the action complete? | -- | Go to Step 9 | --
8 | Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | Go to Step 9 | --
9 | Operate the vehicle within the conditions under which the original symptom was noticed. Does the system now operate properly? | -- | System OK | Go to Diagnostic Aids