How are oil pump issues diagnosed?
When diagnosing a possible loss of oil pressure, the technician will check the oil level first, then the engine will be inspected for engine oil leaks. This is because running low on oil can cause loss of oil pressure, and oil starvation issues. If the oil is full, and there are no leaks, the technician will connect to the vehicle with a computerized scanner to read sensor data, and compare that to actual conditions. Before the technician can suspect any mechanical failure, or start the engine, the engine oil pressure sensor must be proven to function properly. The technician will test the oil pressure sensor and associated electrical circuit, and determine if the sensor should be replaced. If the sensor is reporting correctly, the technician will suspect the engine oil pump, which necessitates removal of the oil pan, and physical inspection.

How is an oil pump replaced?
After a diagnosis is made, if the oil pressure sensor is faulty, it will be resealed (if required) and replaced. If the engine oil pump is suspected, the engine oil pan must be removed. The oil will be drained, and all obstructions must be removed. The oil pan is unbolted, the seal is broken, and the oil pump is confirmed faulty. The new oil pump will be installed according to manufacturer specification, and the oil pan will be replaced. Once all obstructions are replaced, the engine oil is filled, and the engine is turned with the starter without ignition power. If oil pressure builds, the engine can be started and tested.
RepairPal Recommendations for oil pump issues
After the oil pressure indicator light comes on, we do not recommend starting the engine until oil pressure can be confirmed. Continued use of the vehicle after the warning has come on may result in a seized engine due to oil starvation.