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

Tools Required

• 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: Measuring Engine Oil Pressure
Courtesy of GENERAL MOTORS CORP.
IMPORTANT: This test is performed to verify the operation of the oil pressure relief valve. Refer to Cylinder Deactivation (Active Fuel Management) System Description , Lubrication Description - Main Pressure Below 55 psi with Cylinder Deactivation (Active Fuel Management) Off , Lubrication Description - Main Pressure Above 55 psi with Cylinder Deactivation (Active Fuel Management) Off , Lubrication Description - Main Pressure Below 55 psi with Cylinder Deactivation (Active Fuel Management) On , and Lubrication Description - Main Pressure Above 55 psi with Cylinder Deactivation (Active Fuel Management) On .
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 Engine Oil Pressure While Observing Both Gages
Courtesy of GENERAL MOTORS CORP.
4. Install the J 21867  (1), or equivalent to the J-21867-16  . 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 448 kPa (65 psi), both gages should display the same pressure reading. If the readings are not the same and the lower pressure gage (2) has a higher reading, the 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 448 kPa (65 psi), the upper gage (1) should display no greater than 448 kPa (65 psi). If the reading on the upper pressure gage (1) is greater than 448 kPa (65 psi), the oil pressure relief valve is stuck in the closed position.
6. Repair, as required.