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

For equivalent regional tools, refer to Special Tools .

Fig 1: View Of Special Tools Oil Pressure Gage & Adapter
Courtesy of GENERAL MOTORS COMPANY
NOTE:
• Cylinder Deactivation (Active Fuel Management) Oil Pressure Relief Valve Diagnosis and Testing is applicable for RPO LH6/LMG/LY5/LC9/L76/LY2/LY6/L9H.
• 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 .
1. Remove the oil filter and install the EN-47971  gauge adapter (1).
2. Install the J 21867  gauge (2), or equivalent, to the EN-47971  gauge adapter (1).
Fig 2: View Of Oil Pressure Sensor
Courtesy of GENERAL MOTORS COMPANY
3. Remove the oil pressure sensor and install the J-21867-16  adapter.
Fig 3: Measuring Oil Pressure While Observing Both Gages
Courtesy of GENERAL MOTORS COMPANY
4. Install the J 21867  gauge (1), or equivalent, to the J-21867-16  adapter (2).
5. 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.
   NOTE:

   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.
6. Repair, as required.