Oil Pressure Diagnosis and Testing

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Tools Required

J 21867 Pressure Gage. See Special Tools and Equipment .
J 42907 Oil Pressure Testing Tool. See Special Tools and Equipment .

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.
If required, add the recommended grade engine oil and fill the crankcase until the oil level measures full on the oil level indicator.
Run the engine briefly, 10-15 seconds, 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 conditions:
- Oil diluted by water or glycol anti freeze
- Foamy oil
Remove the oil filter and install the J 42907 .
Install J 21867 or equivalent to the J 42907 .

Fig 1: Installing J 21867 To The J 42907 To Measure The Engine Oil Pressure

Courtesy of GENERAL MOTORS CORP.

Run the engine and measure the engine oil pressure.
Compare the readings to Engine Mechanical Specifications (LR4 VIN V) or Engine Mechanical Specifications (LM7 VIN T) or Engine Mechanical Specifications (L59 VIN Z) or Engine Mechanical Specifications (LQ4 VIN U) or Engine Mechanical Specifications (LQ9 VIN N) .
If the engine oil pressure is below specifications, inspect the engine for one 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, Pump Screen and 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.
If the oil pressure reading on the J 21867 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.