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

Special Tools

• EN-47971 Oil Pressure Gauge Adapter
• J 21867 Pressure Gauge
• J-21867-16 Oil Pressure Adapter

Fig 1: Oil Pressure Gage And 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 pan. Refer to Cylinder Deactivation (Active Fuel Management) System Description , and Lubrication Description (with Active Fuel Managment) , Lubrication Description (without Active Fuel Management) .

1. Review the system operation in order to familiarize yourself with the system functions. As required, disable the auto-stop function prior to repair. Refer to Hybrid Modes of Operation Description .
2. Remove the oil filter and install the EN-47971 (1).
3. Install the J 21867 (2), or equivalent to the EN-47971 (1).
Fig 2: View Of Oil Pressure Sensor
Courtesy of GENERAL MOTORS CORP.
4. Remove the oil pressure sensor and install the J-21867-16 .
Fig 3: Measuring Oil Pressure
Courtesy of GENERAL MOTORS CORP.
5. Install the J 21867 (1), or equivalent to the J-21867-16 (2).
6. 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.
   IMPORTANT:

   If both gauges are display equal pressures, but the pressures are low, debris could be present in the oil pressure relief valve causing an intermittent or constant open condition. Check the oil pressure relief valve for debris that could cause the valve to stick open and reduce engine oil flow and/or pressure simultaneously.

   • 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.
7. Repair, as required.