Power Steering Pressure Switch Check. Buick Roadmaster 1996

For 1990-2009 cars
Engine Controls Components
Change/Low Oil, PSP and PNP
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The Power Steering Pressure (PSP) switch is a normally open pressure switch located in the high pressure (outlet) hose of the power steering system. The PCM applies a voltage (about 12.0 Volts) to the sensor. When power steering pressure is low the PSP switch is open and the PCM senses high signal voltage (low engine load). When power steering pressure is high, such as during parking maneuvers, etc., the PSP switch closes, and the PCM senses low signal voltage (high engine load). The PCM will increase the idle air rate and retard the timing to compensate for the additional load on the engine.

### Diagnostic Aids

• | A pressure switch that will not close or an open circuit may cause the engine RPM to drop when power steering loads is high.

• | A switch that will not open or the signal circuit shorted to ground may have an adverse effect on idle quality.

Inspect all related wiring and connectors including the connections at the PCM. These may cause an intermittent malfunction. Check for damaged, corroded or pushed out terminals.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check

2

1. Install the scan tool.
2. Start the engine.

Does the scan tool indicate PSP switch Normal?

--

Go to Step 3

Go to Step 4

3 | Turn the steering wheel and hold momentarily against stop. Does the scan tool indicate PSP switch High Pressure? | -- | Go to Diagnostic Aids | Go to Step 6

4

1. Turn the ignition ON, Engine OFF.
2. Disconnect the PSP switch connector.

Does the scan tool indicate PSP switch Normal?

--

Go to Step 14

Go to Step 5

5

1. Turn the ignition OFF.
2. Disconnect the PCM connector C2.
3. Using a test light (J34142-B) connected to B+, probe the PCM harness connector terminal C2-26.

Is the test light OFF?

--

Go to Step 15

Go to Step 12

6

1. Disconnect the PSP switch connector.
2. Using a fused jumper wire, jumper the two harness connector terminals together.

Does the scan tool indicate PSP switch High Pressure?

--

Go to Step 10

Go to Step 7

7 | Using a fused jumper wire connected to ground, probe the signal circuit terminal in the PSP switch harness connector. Does the scan tool indicate PSP switch High Pressure? | -- | Go to Step 13 | Go to Step 8

8

1. Leave the fused jumper in place.
2. Turn the ignition OFF.
3. Disconnect the PCM connector C2.
4. Using a test light (J 34142-B) connected to B+, probe PCM harness connector terminal C2-26.

Does the test light illuminate?

--

Go to Step 9

Go to Step 11

9 | Check for faulty connections at the PCM. Was condition found and corrected? | -- | Go to Step 16 | Go to Step 15
10 | Check for faulty connections at the PSP switch. Was condition found and corrected? | -- | Go to Step 16 | Go to Step 14
11 | Repair the open PSP signal circuit. Is the repair complete? | -- | Go to Step 16 | --
12 | Repair the PSP signal circuit for a short to ground. Is the repair complete? | -- | Go to Step 16 | --
13 | Repair open PSP ground circuit. Is the repair complete? | -- | Go to Step 16 | --
14 | Replace the PSP switch. Is the repair complete? | -- | Go to Step 16 | --
15 | Important: The replacement PCM must be reprogrammed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the repair complete? | -- | Go to Step 16 | --
16 | Operate the vehicle within the conditions under which the original symptom was noted. Does the system now operate properly? | -- | System OK | Go to Step 2