Oil Pressure Indicator Is Inaccurate

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 1997 GMC Savana Special, 1997 GMC Savana Camper Special, 1997 GMC Savana, 1997 Chevrolet RV Cutaway, and 1997 Chevrolet Cutaway. However, it is still accessible from the selected car via links, so may be relevant.

With engine running, compare oil pressure with oil pressure gauge reading. If readings are reasonably accurate, gauge is operating properly. Check engine. If readings are not reasonably accurate. go to next step.
Disconnect oil pressure sender harness connector. Turn ignition switch to RUN position. Using Tester (J-33431-B), connect Red tester lead to Tan wire terminal of oil pressure sender harness connector and other lead to ground. Adjust tester to 0 ohms and then to 88 ohms. Check oil pressure gauge. Oil pressure gauge should indicate approximately 0 psi and then 80 psi. If gauge indicates correctly, replace oil pressure sender. If gauge does not indicate correctly, go to next step.
Disconnect instrument cluster harness connector. Connect a fused jumper wire between instrument cluster harness connector terminal B17 (Pink wire) and battery power. Connect a second fused jumper wire between instrument cluster harness connector terminal B13 (Black/White wire) and ground. Using Tester (J-33431-B), connect Red tester lead to instrument cluster harness connector terminal No. B8 (Tan wire) and other lead to ground. Adjust tester to zero ohms, and then to 88 ohms. If oil pressure gauge indicates correctly, repair Tan wire. If oil pressure gauges does not indicate correctly, replace instrument cluster. See INSTRUMENT CLUSTER under REMOVAL & INSTALLATION.