GM Service Manual Online
For 1990-2009 cars only
    • With the vehicle on a level surface, allow adequate drain down time (2-3 minutes) and measure for a low oil level.
    • Add the recommended grade engine oil and fill the crankcase until the oil level measures full on the oil level indicator.
    • Run the engine and verify low or no oil pressure on the vehicle gage or light.
    • Listen for a noisy valve train or a knocking noise.
    • Inspect for the following:
       - Oil diluted by moisture or unburned fuel mixtures
       - Improper oil viscosity for the expected temperature
       - Incorrect or malfunctioning oil pressure sender
       - Incorrect or malfunctioning oil pressure gage
       - Plugged oil filter
       - Malfunctioning oil bypass valve
    • Remove the oil pressure sender or another engine block oil gallery plug.
    • Install a oil pressure gage and measure the engine oil pressure.
    • Compare the readings to specifications. Refer to Engine Mechanical Specifications .
    • If the engine oil pressure is below specifications, inspect the engine for one or more of the following:
       - Oil pump worn or dirty
       - Refer to Oil Pump Inspection .
       - Oil pump-to-engine front cover bolts loose
       - Refer to Oil Pump Assemble .
       - Oil pump screen loose, plugged, or damaged
       - Oil pump screen O-ring seal missing or damaged
       - Malfunctioning oil pump pressure regulator valve
       - Excessive bearing clearance
       - Refer to Crankshaft and Bearing Cleaning and Inspection .
       - Cracked, porous or restricted oil galleries
       - Oil gallery plugs missing or incorrectly installed
       - Refer to "Cylinder Block Plug Installation" in this service manual.
       - Broken lash adjusters