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

Special Tools

• 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 .

Fig 1: View Of Special Tools Oil Pressure Gage & Adapter
Courtesy of GENERAL MOTORS CORP.
IMPORTANT:
• Active Fuel Management Oil Pressure Relief Valve Diagnosis and Testing is applicable for RPO LY2/LC9/LY5/LMG/LY6/L76/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 (RPO LY2)  or Lubrication Description (RPO LC9/LY5/LMG)  or Lubrication Description (RPO LY6/L9H)  or Lubrication Description (RPO L76) .
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 2: View Of Oil Pressure Sensor
Courtesy of GENERAL MOTORS CORP.
3. Remove the oil pressure sensor and install the J-21867-16  . See Special Tools .
Fig 3: Measuring Oil Pressure While Observing Both Gages
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 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.