To diagnose oil pressure problems, check oil levels with the vehicle's dip stick, determine whether you have the right type of oil for the season of the year, examine the oil pump screen, assess whether crankshaft journals or rod bearings need replacement, and determine if the car's instrumentation is functioning correctly. Determine the cause of low oil pressure immediately to prevent major engine damage. Rapping or knocking noises from the engine are a sign of imminent engine failure.
If engine oil is low, the engine may have a leak or be burning oil. Engine leaks may mean that gaskets need replacement. An engine that is burning oil may need to have its crankshaft journals and rod bearings replaced.
If oil levels are adequate, check the oil viscosity to ensure it is appropriate for the season. High viscosity oil is needed during warm weather, while low viscosity oil is best for cold weather. Using low viscosity oil during the summer results in low oil pressure.
Next, determine whether the oil pump screen is clear by removing the sump tank. Remove any dirt and debris to restore proper oil pressure. Also, check the pickup tube to ensure it is not blocked and is mounted correctly.
Determine whether the car's instrumentation is malfunctioning by disconnecting the pressure sending unit. If the warning light remains on or the gauge reading does not change while the unit is disconnected, the unit needs replacing, and probably nothing is wrong with the engine.