2002 Oldsmobile Bravada motor dies

Well, theoretically, when you turn your a/c on the idle is supposed to raise a bit too. This is why they always say, "the a/c uses up gas" because the idle has to raise in order to keep the car running. The idle air control valve should adjust the idle when you turn it on. The oil pressure is another problem all by itself, I dont know if you your oil is low, or the sending unit is just bad and is giving a false reading. Or that you may need a new pump. The repair shop will have to determine that.