Oil Pressure Diagnosis and Testing

Special Tools

• EN-21867  Pressure Gauge
• EN-21867-16  Oil Pressure Adapter

For equivalent regional tools, refer to Special Tools .

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 the 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 gauge or light.
4. Listen for a noisy valve train or a knocking noise.
5. Inspect for the following conditions:
   • Oil diluted by water or glycol antifreeze

     Refer to Coolant in Engine Oil .

   • Foamy oil, which may be caused by a cut or damaged oil pump screen O-ring seal
Fig 1: Oil Pressure Sensor
Courtesy of GENERAL MOTORS COMPANY
6. Remove the oil pressure sensor (1).
Fig 2: Engine Oil Pressure Gauge & Adapter
Courtesy of GENERAL MOTORS COMPANY
7. Install the EN-21867-16  adapter (2) and EN-21867  pressure gauge (1), or equivalent.
8. Run the engine until the engine reaches normal operating temperature and measure the engine oil pressure.
9. Compare the readings to Engine Mechanical Specifications (RPO LMG VIN 0) , Engine Mechanical Specifications (RPO L9H) , Engine Mechanical Specifications (RPO L94 VIN F) , Engine Mechanical Specifications (RPO L96 VIN G) , Engine Mechanical Specifications (RPO LC9 VIN 7) .
10. If the engine oil pressure is below specifications, inspect the engine for 1 or more of the following conditions:
    • If equipped, valve lifter oil manifold filter plugged or damaged. Refer to Valve Lifter Oil Manifold Cleaning and Inspection .
    • If equipped, improper operation of the active fuel management oil pressure relief valve. Refer to Cylinder Deactivation (Active Fuel Management) Oil Pressure Relief Valve Diagnosis and Testing .
    • If equipped, check if the engine oil cooler or oil cooler lines are plugged or damaged.
    • Oil pump worn or dirty. Refer to Oil Pump Cleaning and Inspection .
    • Oil pump-to-engine block bolts loose. Refer to Oil Pump, Screen and Crankshaft Oil Deflector Installation .
    • Oil pump screen loose, plugged, or damaged.
    • Oil pump screen O-ring seal missing or damaged.
    • Excessive debris in the oil pan and/or oil filter (possibly indicating internal engine damage).
    • Malfunctioning oil pump pressure relief valve.
    • Excessive bearing clearance and/or bearing damage. Refer to Crankshaft and Bearing Cleaning and Inspection , and Camshaft and Bearings Cleaning and Inspection .
    • Cracked, porous, or restricted oil galleries.
    • Oil gallery plugs missing or incorrectly installed. Refer to Engine Block Plug Installation .