Oil Pressure Diagnosis and Testing

Tools Required

• J 21867  Pressure Gage. See Special Tools and Equipment .
• J 36648-A  Oil Pressure Gage Adapter. See Special Tools and Equipment .

1. With the vehicle on a level surface, run the vehicle for a few minutes, allow adequate drain down time, 2-3 minutes, and measure for a low oil level.
2. If required, add the recommended grade engine oil and fill the crankcase until the oil level measures full on the oil level indicator.
3. Run the engine briefly, 10-15 seconds, and verify low or no oil pressure on the vehicle gage or light.
4. Listen for a noisy valve train or a knocking noise.
5. Inspect for the following:
   • Foamy oil
   • Slow idle speed
   • Plugged oil filter
   • Oil diluted by the following:
     • Water
     • Engine coolant
     • Unburned fuel mixtures
   • Malfunctioning oil filter bypass valve
   • Incorrect or faulty oil pressure gage
   • Incorrect or faulty oil pressure gage sensor
   • Improper engine oil viscosity for the expected temperature
Fig 1: View Of Oil Pressure Sensor Wiring Harness
Courtesy of GENERAL MOTORS CORP.
6. Disconnect the oil pressure sensor wiring harness.
Fig 2: Identifying Oil Pressure Sensor
Courtesy of GENERAL MOTORS CORP.
7. Remove the oil pressure sensor.
8. Install the J 21867  with the J 36648-A  adapter. See Special Tools and Equipment .
9. Measure the engine oil pressure.
10. Compare the readings to the Engine Mechanical Specifications .
11. If the engine oil pressure is below specifications, inspect the engine for one or more of the following:
    • Loose oil filter adapter bolts
    • Missing or damaged oil filter adapter O-ring seal or seals
    • Worn or dirty oil pump
    • Loose oil pump-to-engine block bolts
    • Loose, plugged or damaged oil pump screen
    • Missing or damaged oil pump screen O-ring seal
    • Damage or leak in the oil pump screen suction tube
    • Malfunctioning oil pump pressure regulator valve
    • Missing or incorrectly installed oil gallery plugs
    • Loose camshaft intermediate drive shaft bolts
    • Excessive bearing clearance for the following:
      • Connecting rod or rods
      • Crankshaft
      • Camshaft or camshafts
      • Camshaft intermediate drive shaft sprocket
    • Cracked, porous or restricted oil galleries
    • Broken valve lifters
12. Repair or replace components as necessary.