1999 Dodge Caravan oil pressure

My 1999 dodge caravan with a 3.8l. Engin starts fine, good oil pressure. After about 15 minutes of running I get a oil light warning and the lifters begin to rattle. Could this be the oil pump or a friend told me that there is a oil pressure control valve inside the pan that controls the oil pressure so that oil gets to the top of the motor. Please help! Thank you in advance.

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