Oil Pressure Diagnosis and Testing (L98, LS2, L76, L77)

Special Tools

• EN-47971  Oil Pressure Gauge Adapter
• J 21867  Pressure Gauge

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 anti freeze
   • Foamy oil
Fig 1: Locating EN-47971 & J 21867
Courtesy of GENERAL MOTORS CORP.
6. Remove the oil filter and install the EN-47971  oil pressure gauge adapter (1).
7. Install J 21867  pressure gauge (2), or equivalent, to the EN-47971  oil pressure gauge adapter (1).
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 (L77) .
10. If the engine oil pressure is below specifications, inspect the engine for one or more of the following conditions:
    NOTE:

    Engines equipped with an oil pressure sensor, active fuel management and/or variable valve timing can demand more oil pressure, than the minimum requirements for other mechanical engine components, to operate properly. Verify that the oil pressure sensor is operating correctly. If the engine oil pressure meets the minimum specifications but there is still an oil pressure concern and/or a MIL is encountered due to DTCs P0011 or P0521, inspect the engine for 1 or more of the following conditions:

    • Valve lifter oil manifold filter plugged or damaged.

      Refer to Valve Lifter Oil Manifold Cleaning and Inspection .

    • 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 (LS3, L76, L77) .

    • Oil pump-to-engine block bolts loose.

      Refer to Oil Pump, Screen and Crankshaft Oil Deflector Installation .

    • Oil pump screen loose, plugged, or damaged. Refer to Oil Pump Cleaning and Inspection (LS3, L76, L77) .
    • Oil pump screen O-ring seal missing or damaged. Refer to Oil Pump Cleaning and Inspection (LS3, L76, L77) .
    • Oil filter loose or a leaking or damaged gasket. Refer to Oil Filter, Adapter, and Pan Cover Installation .
    • Malfunctioning oil pump pressure relief valve. Refer to Oil Filter, Adapter, and Pan Cover Installation .
    • Above acceptable bearing clearance. Refer to Engine Block Plug Removal .
    • Cracked, porous, or restricted oil galleries. Refer to Engine Block Plug Installation .
    • Oil gallery plugs missing or incorrectly installed.

      Refer to Engine Block Plug Installation .

    • Broken valve lifters. Refer to Valve Lifter Replacement .
    NOTE:

    The following step applies to L76 engines equipped with active fuel management.

    • 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 .

      Repair as necessary.

11. If the oil pressure reading on the J 21867  pressure gauge (2), or equivalent, is within specifications, inspect for the following conditions:
    • Plugged or incorrect oil filter and/or malfunctioning oil filter bypass valve. Refer to Engine Oil and Oil Filter Replacement .
    • Malfunctioning engine oil pressure sensor or switch. Refer to Engine Oil Pressure Sensor and/or Switch Replacement .