what is the possible causes for low engine oil pressure?

If the pump is working well, worn bearings have a larger than spec. gap & alotta flow past'em.

Make sure that there's enough oil in the system in the first place. I know you've probably already checked it, but you'd be surprised at how many times while working at a certain national oil and lube company people would come in with their oil pressure lights on and no oil in the engine. Other than that, the gentleman who responded before me pretty much covered it.

Oil pump, oil pump seal (using too heavy of an oil can fracture the seal), oil filter clogged and oil not circulating properly past the sending unit. Or bad sending unit instead of oil pressure.

Low oil level, dirty oil filter, dirty oil, broken oil pump, clogged oil pan screen, clogged oil passage.

=Low oil level.=

Perhaps faulty oil pump, kinked oil hose, or faulty oil pressure gauge.

first check the screen on the oil pump.if not the problem cam bearings or crank bearings

too thin of oil,bearing clearance,plugged return holes in head, bad sending unit,no oil,plugged filter,

i agree with the previous replies . also

if your oil pickup is clogged with particulate matter.