Oil Pressure Diagnosis and Testing

Tools Required

• J 21867  Pressure Gage. See Special Tools .
• J 42907  Oil Pressure Tester. See 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 gage 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
   • Foamy oil
6. Remove the oil filter and install the J 42907  . See Special Tools .
   Fig 1: Installing J 21867 To The J 42907 To Measure The Engine Oil Pressure

   Courtesy of GENERAL MOTORS CORP.
7. Install the J 21867  , or equivalent to the J 42907  . See Special Tools .
8. Run the engine and measure the engine oil pressure.
9. Compare the readings to Engine Mechanical Specifications (LR4 VIN V) , Engine Mechanical Specifications (LM7 VIN T) , Engine Mechanical Specifications (L33 VIN B) , Engine Mechanical Specifications (L59 VIN Z) , Engine Mechanical Specifications (LQ4 VIN U)  or Engine Mechanical Specifications (LQ9 VIN N) .
10. If the engine oil pressure is below specifications, inspect the engine for 1 or more of the following conditions:
    • 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
    • Malfunctioning oil pump pressure relief valve
    • Excessive bearing clearance
    • Cracked, porous, or restricted oil galleries
    • Oil gallery plugs missing or incorrectly installed

      Refer to Engine Block Plug Installation .

    • Broken valve lifters

      Repair as necessary.

11. If the oil pressure reading on the J 21867  (see Special Tools ) or equivalent, is within specifications, inspect for the following conditions:
    • Plugged or incorrect oil filter and/or malfunctioning oil bypass valve
    • Malfunctioning oil pressure gage or sensor

      Repair, as necessary.