How do you know if you have an AFM 5.3 engine? I have a 2006 GMC SLE 1500 4WD 5.3L coming in the shop later this week with oil pressure that goes from pegged at 80PSI to 0PSI on dash gauge. VIN# is 1GTEK14T66Z103406. I went to the ALLDATA lubrication diagrams ... Login to read more.