Low oil pressure - 2003 Ford Expedition

Have you checked with a mechanical gauge to see what your pressure is? You might actually have low oil pressure.

Do you mean what causes low oil pressure? This is a very reliable engine for the most part. If the oil light is on or gauge is reading low, have the oil pressure sensor inspected for failure. These sensors do go bad.

low oil pressure caused by worn engine bearings and faulty oil pump or oil pump pick up screen clogged with sludge.if oil pressure low engine will knock.check oil pressure oil pressure sending unit could be bad.

What are you going by to determine it has low oil pressure ? Instrument cluster gauge , low oil light ? Have you had a mechanical pressure gauge hooked to see what the pressure really is ?

No, the oil level nothing to do with the pressure.
If you have low pressure, check the sender unit, check the pressure with a mechanical gauge, if still low, check the pump

first thing check is the engine oil level.if oil level okay check oil pressure should be for the 4.2 engine oil pressure should be 12 psi @ 1200 rpm for the 5.3 oil pressure should be 18 psi @ 2000 rpm if oil pressure good problem in the oil pressure sending unit. if oil pressure is low problem faulty oil pump or worn crankshaft bearings if oil pressure low engine will have rod knock.make sure you are using correct oil viscosity if oil too thick you will have low oil pressure oil too thin you will loose oil pressure.

Low oil pressure at idle can be caused by an engine with worn rod or main bearings due to (usually) high mileage . This however does not mean the engine is still not serviceable as long as the oil pressure is low only at idle. The pressure should at minimum get into the normal range at anything above idle speed.Not much oil pressure is really necessary at LOW speed. At low speed, as long as there is oil getting to the bearings, even at low pressure, you are OK. In a high mileage engine the oil pressure is often low at idle simply because the oil pump is turning slowly and cannot maintain higher pressure between the larger than normal crankshaft and bearing clearances. As speed increases the pump turns faster and supplies more oil and the pressure should go higher. Low pressure as long as it is only at idle is not a problem. However at higher speeds the pressure should be in the normal range. Such a worn engine can benefit from higher viscosity (thicker) oil such as 20W-50 in above freezing weather and 10W-40 in winter. That will increase idle pressure and the thicker oil film maintains a better film between the worn parts

It means the sensor that detects your oil pressure has seen a situation where the oil pressure is too low and engine damage will result. Could be just a bad sensor, but better have it checked with a mechanical gauge to see exactly what the pressure is.

Check your oil, it may be low if not the oil pressure needs checked. The sending switch could be bad or you have low oil pressure. If you have low oil pressure have it fixed ASAP. The loss of oil pressure can cause severe engine damage.

If low oil pressure is verifiable the only repair is replacement of the oil pump assembly.

Start by verifying oil pressure with a mechanical oil pressure gauge. If oil pressure is low then replace oil pump.