GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2000 🢒 GL7 (Export) 🢒 Engine 🢒 Engine Controls - 3.0L (LW9) 🢒 Engine Oil Pressure Sensor and/or Switch Diagnosis

Circuit Description

The engine oil pressure switch is normally closed. When engine oil pressure increases above 5 psi the switch contacts open. The PCM supplies 12  volts to the oil pressure input circuit. With low oil pressure the 12 volts is pulled low to ground.

When the PCM monitors a low oil pressure condition the PCM will command a message be displayed on the IPC.

Message Conditions
    • Engine speed is more than 57 RPM for 4 seconds.
    • The engine oil pressure switch indicates low oil pressure for 4.2 seconds.

The Message is cleared when the engine oil pressure switch indicates oil pressure or when engine speed is 0 RPM.

Step

Action

Values

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. Turn ON the ignition while leaving the engine OFF.
  2. Observe the engine oil pressure scan tool display.

Does the display indicate engine oil pressure is LOW?

--

Go to Step 3

Go to Step 6

3

Start and idle the engine.

Does the display indicate engine oil pressure is OK?

--

System OK

Go to Step 4

4
  1. Turn OFF the ignition switch.
  2. Disconnect the engine oil pressure switch.
  3. Turn ON the ignition while leaving the engine OFF.

Does the display indicate engine oil pressure is OK?

--

Go to Step 8

Go to Step 5

5
  1. Turn OFF the ignition switch.
  2. Disconnect the PCM.
  3. Test the engine oil pressure signal circuit for a shorted to ground condition. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 2

Go to Step 12

6
  1. Turn OFF the ignition switch.
  2. Disconnect the engine oil pressure switch connector.
  3. Jumper the engine oil pressure signal circuit to a known good ground using a fused jumper.
  4. Turn ON the ignition while leaving the engine OFF.

Does the display indicate engine oil pressure is LOW?

--

Go to Step 9

Go to Step 7

7
  1. Turn OFF the ignition switch.
  2. Disconnect the PCM.
  3. Test the engine oil pressure signal circuit for an open, high resistance or, if the jumper fuse is blown, a short to voltage condition. Refer to Wiring Repairs in Wiring Systems.

Did you find and repair the condition?

--

Go to Step 2

Go to Step 11

8

Test the engine oil pressure with a mechanical pressure gauge. Refer to Oil Pressure Diagnosis and Testing in Engine Mechanical. Ensure the engine oil pressure never drops below the closing pressure of the switch.

Is the correct engine oil pressure indicated?

--

Go to Step 10

Go to Oil Pressure Diagnosis and Testing

9

Inspect for proper terminal contact at the engine oil pressure switch connector. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 2

Go to Step 10

10

Replace the engine oil pressure switch.

Did you complete the replacement?

--

Go to Step 2

--

11

Inspect for proper terminal contact at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 2

Go to Step 12

12

Important: :  The replacement PCM must be programmed.

Replace the PCM. Refer to Powertrain Control Module Replacement/Programming .

Did you complete the replacement?

--

Go to Step 2

--