Cylinder Deactivation (Active Fuel Management) Oil Pressure Relief Valve Diagnosis and Testing

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Special Tools

Fig 1: Checking Oil Pressure

Courtesy of GENERAL MOTORS COMPANY

NOTE:

This test is performed to verify the operation of the active fuel management oil pressure relief valve located in the oil pan. Refer to Cylinder Deactivation (Active Fuel Management) System Description , and Lubrication Description (L76, L77) .

Remove the oil filter and install the EN-47971 oil pressure gauge adapter (1).
Install the J 21867 pressure gauge (2), or equivalent, to the EN-47971 oil pressure gauge adapter (1).

Fig 2: Oil Pressure Sensor

Courtesy of GENERAL MOTORS COMPANY

Fig 3: Testing Oil Pressure

Courtesy of GENERAL MOTORS COMPANY

Install the J 21867 pressure gauge (1), or equivalent, to the J-21867-16 oil pressure adapter (2).
Run the engine and measure the engine oil pressure while observing both gauges.
Operate the throttle, as required, to increase and decrease the engine oil pressure.
- With the engine running and the lower pressure gauge (2) measuring below 379 kPa (55 psi), both gauges should display the same pressure reading. If the readings are not the same and the lower gauge (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 gauge (2) measuring above 379 kPa (55 psi), the upper gauge (1) should display no greater than 379-517 kPa (55-75 psi). If the reading on the upper gauge (1) is greater than 517 kPa (75 psi), the active fuel management oil pressure relief valve is stuck in the closed position.
Repair, as required.