Chevrolet Silverado / GMC Sierra. Service manual — part 236

1. Remove the oil filter and install the EN-47971 (1). See Special Tools.

2. Install the J 21867 (2), or equivalent, to the EN-47971 (1). See Special Tools.

Fig. 17: Oil Pressure Sensor
Courtesy of GENERAL MOTORS CORP.

3. Remove the oil pressure sensor and install the J-21867-16 . See Special Tools.

pan. Refer to Lubrication Description.

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2

Fig. 18: Measure Engine Oil Pressure
Courtesy of GENERAL MOTORS CORP.

4. Install the J 21867 (1), or equivalent, to the J-21867-16 (2). See Special Tools.

5. Run the engine and measure the engine oil pressure while observing both gages.

Operate the throttle, as required, to increase and decrease the engine oil pressure.

With the engine running and the lower pressure gage (2) measuring below 379 kPa (55
psi), both gages should display the same pressure reading. If the readings are not the

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2

same and the lower gage (2) has a higher reading, the active fuel management oil
pressure relief valve is stuck in the open position or the valve lifter oil manifold filter
is plugged.

With the engine running and the lower pressure gage (2) measuring above 379 kPa (55
psi), the upper gage (1) should display no greater than 379-517 kPa (55-75 psi). If the
reading on the upper gage (1) is greater than 517 kPa (75 psi), the active fuel
management oil pressure relief valve is stuck in the closed position.

6. Repair, as required.

CAMSHAFT POSITION ACTUATOR AND SOLENOID VALVE DIAGNOSIS AND TESTING

1. Measure the engine oil level. Fill, as required.

2. Using the scan tool, inspect for diagnostic codes within the engine control module (ECM).

Refer to Diagnostic System Check - Vehicle . Repair, as required.

3. Verify proper engine oil pressure and operation of the active fuel management oil pressure

relief valve. Refer to Oil Pressure Diagnosis and Testing.

4. Inspect the camshaft position (CMP) actuator solenoid valve for proper operation. Refer to

Camshaft Position Actuator Solenoid Valve Inspection (On-Vehicle) or

Camshaft

Position Actuator Solenoid Valve Inspection (Off-Vehicle)

.

If valve inspection confirms proper movement of the spool, replace the CMP actuator
and CMP valve.

If valve inspection confirms improper movement of the spool, replace only the CMP
valve.

5. Verify proper operation of the CMP actuator control system. Refer to Diagnostic Starting

Point - Engine Controls .

OIL LEAK DIAGNOSIS

Step

Action

Yes

No

IMPORTANT:

You can repair most fluid leaks by first visually locating the leak, repairing or replacing the
component, or by resealing the gasket surface. Once the leak is identified, determine the cause of
the leak. Repair the cause of the leak as well as the leak itself.

1

1. Operate the vehicle until it reaches normal

operating temperature.

2. Park the vehicle on a level surface, over a

large sheet of paper or other clean surface.

3. Wait 15 minutes.

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2

4. Inspect for drippings.

Are drippings present?

Go to Step 2

System OK

2

Can you identify the type of fluid and the

approximate location of the leak?

Go to Step 10

Go to Step 3

3

1. Visually inspect the suspected area. Use a

small mirror to assist in looking at hard to

see areas.

2. Inspect for leaks at the following locations:

Sealing surfaces

Fittings

Cracked or damaged components

Can you identify the type of fluid and the

approximate location of the leak?

Go to Step 10

Go to Step 4

4

1. Completely clean the entire engine and

surrounding components.

2. Operate the vehicle for several kilometers,

miles, at normal operating temperature and

at varying speeds.

3. Park the vehicle on a level surface, over a

large sheet of paper or other clean surface.

4. Wait 15 minutes.

5. Identify the type of fluid, and the

approximate location of the leak.

Can you identify the type of fluid and the

approximate location of the leak?

Go to Step 10

Go to Step 5

5

1. Visually inspect the suspected area. Use a

small mirror to assist in looking at hard to

see areas.

2. Inspect for leaks at the following locations:

Sealing surfaces

Fittings

Cracked or damaged components

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2