Oil Pressure Relief Valve Diagnosis and Testing

Special Tools

• EN-47971  Oil Pressure Gauge Adapter. See Special Tools .
• J 21867  Pressure Gauge
• J-21867-16  Oil Pressure Adapter. See Special Tools .

Fig 1: Oil Pressure Gauge & Adapter
Courtesy of GENERAL MOTORS CORP.
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 Lubrication Description .
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: 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
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 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.
6. Repair, as required.