GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1998 🢒 DeVille 🢒 Engine 🢒 Engine Controls - 4.0L and 4.6L 🢒 Low Engine Oil Pressure Indicator Diagnosis

Circuit Description

The engine oil pressure switch is normally closed. When engine oil pressure increases above 1 to 4.5 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 Driver Information Center (DIC) or IPC depending upon vehicle model. The PCM will also increase the Desired Idle engine speed in an attempt to raise engine oil pressure.

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.

Idle Speed Increase Conditions
    • Engine speed is more than 400 RPM for 3 seconds.
    • The engine oil pressure switch indicates low oil pressure for 3 seconds.

The Desired Idle speed is commanded to a mininum engine speed of 744 RPM.

Desired Idle is returned to normal PCM control when the engine oil pressure switch indicates oil pressure or when engine speed is 0 RPM.

Test Description

  1. If the Oil Pressure parameter indicates OK when disconnected measure the engine oil pressure with a mechanical gauge. Ensure that engine oil pressure is within operating specifications before replacing the Engine Oil Pressure Switch.

    2.

  2. If the fuse in the jumper opens when probing the circuit repair the short to voltage on the oil pressure input circuit.

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. Turn the ignition ON while leaving the engine OFF.
  2. Connect a scan tool.
  3. Observe the Oil Pressure scan tool data status.

Does the Oil Pressure status indicate LOW pressure?

--

Go to Step 3

Go to Step 6

3

Start and idle the engine.

Does the Oil Pressure status indicate oil pressure is OK?

--

System OK

Go to Step 4

4

  1. Turn the ignition OFF.
  2. Disconnect the Engine Oil Pressure switch connector.
  3. Turn the ignition ON while leaving the engine OFF.
  4. Observe the Oil Pressure scan tool data status.

Does the Oil Pressure status indicate oil pressure is OK?

--

Go to Step 15

Go to Step 5

5
  1. Record the fluid life indexes.
  2. Turn the ignition OFF and wait 30 seconds.
  3. Disconnect PCM connector C2.
  4. Using DMM J 39200 measure the resistance to ground on the oil pressure input circuit.

Is the resistance the same or more than the value specified?

10K ohms

Go to Step 17

Go to Step 11

6

  1. Turn the ignition OFF.
  2. Disconnect the Engine Oil Pressure switch connector.
  3. Using a fused jumper connect the Engine Oil Pressure switch connector terminals A and B together.
  4. Turn the ignition ON while leaving the engine OFF.
  5. Observe the Oil Pressure scan tool data status.

Does the Oil Pressure status indicate LOW pressure?

--

Go to Step 15

Go to Step 7

7
  1. Jumper the oil pressure input circuit to a known good ground.
  2. Observe the Oil Pressure scan tool data status.

Does the Oil Pressure status indicate LOW pressure?

--

Go to Step 12

Go to Step 8

8
  1. Remove the jumper.
  2. Using DMM J 39200 measure the voltage on the oil pressure input circuit.

Is the voltage the within a half volt of the value specified?

B+

Go to Step 9

Go to Step 10

9
  1. Record the fluid life indexes.
  2. Turn the ignition OFF and wait 30 seconds.
  3. Disconnect PCM connector C2.
  4. Turn the ignition ON.
  5. Using DMM J 39200 measure the voltage on the oil pressure input circuit.

Is the voltage more than the value specified?

0.5 volts

Go to Step 13

Go to Step 17

10
  1. Record the fluid life indexes.
  2. Turn the ignition OFF and wait 30 seconds.
  3. Disconnect PCM connector C2.
  4. Turn the ignition ON.
  5. Using DMM J 39200 measure the resistance of the oil pressure input circuit.

Is the resistance the same or less than the value specified?

5 ohms

Go to Step 17

Go to Step 14

11

Repair the short to ground on the oil pressure input circuit.

Is the repair complete?

--

Go to Powertrain Control Module Diagnosis

--

12

Repair the open in the oil pressure switch ground circuit.

Is the repair complete?

--

Go to Powertrain Control Module Diagnosis

--

13

Repair the short to voltage on the oil pressure input circuit.

Is the repair complete?

--

Go to Powertrain Control Module Diagnosis

--

14

Repair the open in the oil pressure input circuit.

Is the repair complete?

--

Go to Powertrain Control Module Diagnosis

--

15
  1. Check the terminal contact at the Engine Oil Pressure switch connector.
  2. Repair terminal contact if needed.

Was terminal contact repaired?

--

Go to Powertrain Control Module Diagnosis

Go to Step 16

16

Replace the Engine Oil Pressure Switch.

Is the replacement complete?

--

Go to Powertrain Control Module Diagnosis

--

17
  1. Check terminal contact at the PCM connector.
  2. Repair terminal contact if needed.

Was terminal contact repaired?

--

Go to Powertrain Control Module Diagnosis

Go to Step 18

18

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

Is the replacement complete?

--

Go to Powertrain Control Module Diagnosis

--