I have a 2003 350z with 128k miles. Every time I start it up the red oil pressure lights comes on for about 3 seconds and then completely goes away. The light comes on regardless if the car is warm or cold but goes away and never comes on when driving. I have checked the oil pressure with a manual gauge and it had good oil pressure. Could it be the oil pressure sending unit I bought a cheap one not a Nissan OEM unit. Or is it worse than that possibly a bad oil pump? any input is greatly appreciated.