PSP Switch Diagnosis. Chevrolet Metro 1998

For 1990-2009 cars
Engine Controls Components
Cell 21: Idle-Up Signals
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The power steering pressure (PSP) switch is normally open to ground. Turning the steering wheel increases 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 before the load on the engine causes a undesirable idle condition. The powertrain control module (PCM) increases the throttle valve opening in order to maintain 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

A PSP switch that does not close, or 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 or a signal line shorted to ground may affect idle quality.

An intermittent malfunction may be caused by a fault in the power steering pressure switch electrical circuit. Inspect the wiring harness and components for any of the following conditions:

• | Backed out terminals.

• | Improper mating of terminals.

• | Broken electrical connector locks.

• | Improperly formed or damaged terminals.

• | Faulty terminal to wire connections.

• | Physical damage to the wiring harness.

• | A broken wire inside the insulation.

• | Corrosion of electrical connections, splices, or 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 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 poor ground connection at the power steering pump or a faulty PSP switch.

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 normal operating temperature is attained.
4. Turn OFF all accessories.
5. Monitor the 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?

--

PSP switch is functioning normally

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 (harness side) with a DMM.

Was 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 (switch side) 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.

Was the test lamp ON when the steering wheel was turned all the way to the right or left?

--

Go to Diagnostic Aids

Go to Step 6

5

1. Check for an open or 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 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 9 | --
9 | 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