Gauge Reading Inaccurate
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 1991 GMC Pickup, 1991 GMC Cab & Chassis, 1991 GMC C3500 HD, 1991 Chevrolet Pickup, and 1991 Chevrolet Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
Disconnect lead from oil pressure sending unit. Connect Gauge Tester (J-24538-A) to lead and ground. Turn ignition on. If gauge reads accurately when connected to tester, replace oil pressure sending unit. If gauge still reads inaccurately, replace oil pressure gauge.