Chevrolet Silverado / GMC Sierra. Manual - part 235
OIL PRESSURE DIAGNOSIS AND TESTING
Tools Required
EN-47971 Oil Pressure Gage Adapter. See Special Tools.
J 21867 Pressure Gage. See Special Tools.
Test
Piston and rings improperly installed or not fitted to the
cylinder bore
2008 Hummer H2
2008 ENGINE Engine Mechanical - 6.2L - H2
Fig. 15: View Of Special Tools Oil Pressure Gage & Adapter
Courtesy of GENERAL MOTORS CORP.
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.
2008 Hummer H2
2008 ENGINE Engine Mechanical - 6.2L - H2
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
6. Remove the oil filter and install the EN-47971 (1). See Special Tools.
7. Install the J 21867 (2), or equivalent to the EN-47971 (1). See Special Tools.
8. Run the engine and measure the engine oil pressure.
9. Compare the readings to Engine Mechanical Specifications.
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 .
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 .
CYLINDER DEACTIVATION (ACTIVE FUEL MANAGEMENT) OIL PRESSURE RELIEF VALVE
VALVE DIAGNOSIS AND TESTING
Tools Required
2008 Hummer H2
2008 ENGINE Engine Mechanical - 6.2L - H2
EN-47971 Oil Pressure Gage Adapter. See Special Tools.
J 21867 Pressure Gage. See Special Tools.
J-21867-16 Oil Pressure Adapter. See Special Tools.
Diagnosis and Testing
Fig. 16: View Of Special Tools Oil Pressure Gage & Adapter
Courtesy of GENERAL MOTORS CORP.
IMPORTANT: This test is performed to verify the operation of the active
fuel management oil pressure relief valve located in the oil
2008 Hummer H2
2008 ENGINE Engine Mechanical - 6.2L - H2