If your vehicle is showing red oil pressure warning light stays on, here are the most likely causes and the parts you'll need to fix each one.
The engine has lost oil due to a leak or burning it over time. Without enough oil in the pan, the pump draws in air and cannot build pressure.
The sensor that measures oil pressure has failed internally or clogged, sending a false zero-pressure warning to the dashboard while actual engine pressure is normal.
A defective filter, incorrect filter type, or a 'double gasket' left behind from a recent oil change is causing a massive pressure drop or leak.
Neglected oil changes cause thick sludge to form, which clogs the screen on the oil pump pickup tube and starves the engine of oil.
High mileage or previous oil starvation has worn down the internal engine bearings (main and rod bearings), creating too much clearance for the pump to maintain pressure.
The mechanical oil pump itself has worn out or its internal pressure relief valve is stuck open, preventing it from pumping oil through the engine.