Where is the oil pressure sensor located on 2003 Sierra 5.3?

 

Behind the intake manifold, it's the connector on the rear driver's side of the block. There are two there - the one with the right-angle connector is the cam position sensor, the one that sticks straight up is the oil pressure sensor.

 

Should be at the back driver side of the block. On top, the manifold is actually cut out to let it thread into the block.