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Gm did report during the 1991 and 1995 years, oil pressure sending units that were incorrect calibrated. It is possible you do have bad sender. I do however always advise a customer with low oil pressure to have a remote guage hooked up and test oil pressure to confirm sender is bad or actual oil pressure problem exists. I will see what info i can get and send shortly about the sender and location
File In Section: 6 - Engine Bulletin No. 47-61-49 Date: December, 1994 Subject: Oil Pressure Gauge Reading Concerns (Replace Oil Pressure Sending Unit) Models: 1991-94 Chevrolet and GMC Truck C/K, S/T, P Models, M/L, G Vans 1991-92 Oldsmobile Bravada with 2.2L, 4.3L, 5.0L, 5.7L, 7.4L Engines (VINs 4, Z, H, K, N - RPOs LN2, LB4, L03, L05, L19) CONDITION Some owners may comment on one or all of the following conditions: ^ High oil pressure when starting engine cold. ^ Low oil pressure when engine is at idle hot. ^ Erratic gauge readings. CAUSE Oil pressure sending unit was not optimally calibrated for all operating conditions. CORRECTION If actual oil pressures are within tolerances listed in Section 6A of the Service Manual, and gauge circuit electrical diagnostics in Section SC of the Service Manual do not uncover the source of the problem, an improved oil pressure sending unit should be installed.
DESCRIPTION PART NUMBER Oil Pressure Sending Unit 12553175
the sender is located back near distributor on top of engine. It will be about2.5" long, 1" in diameter and the top of the sender is made of plastic. Little hard to get to and,, there is a special socket for this you can get at most any parts store. You may? be able to unscrew it with regular set of large pliers. It is a little hard to see but is item #5 in the picture