Engine Oil Pressure Gauge Inaccurate/Inoperative

1. Perform SYSTEM CHECK  . Go to next step.
2. Run engine to operating temperature. Turn engine OFF. Remove oil pressure gauge switch. Install appropriate oil pressure testing gauge into engine. Start engine and let idle. If oil pressure is greater than 21.7 psi (150 kPa), go to next step. If oil pressure is less than 21.7 psi (150 kPa), diagnose and repair low oil pressure problem. See appropriate article in ENGINES.
3. If oil pressure gauge is working but inaccurate, go to step  7 . If gauge reads properly, go to next step.
4. Disconnect oil pressure gauge switch connector. Turn ignition to ON position. Use DVOM to measure voltage between ground and oil pressure gauge switch connector terminal No. 1 (Blue/Yellow wire). If battery voltage is indicated, go to next step. If battery voltage is not indicated, go to step  6 .
5. Use DVOM to measure resistance between ground and oil pressure gauge switch connector terminal No. 1 (Blue/Yellow wire). If reading is 5 ohms or less, go to step  8 . If reading is greater than 5 ohms, go to step  9 .
6. Remove instrument cluster from instrument panel. See INSTRUMENT CLUSTER  under REMOVAL & INSTALLATION. Use DVOM and measure resistance between oil pressure gauge switch connector C2 terminal No. 1 and gauge cluster connector terminal No. 26 (Blue/Yellow wire). See Fig 1 . If reading is 0-5 ohms, go to step  10 . If reading is not 0-5 ohms, go to step  11 .
7. Reconnect instrument cluster and gauge cluster connector. Connect a signal generator tool, an appropriate resistor or a potentiometer between oil pressure gauge switch connector terminal No. 1 (Blue/Yellow wire) and ground. See WIRING DIAGRAMS  . Ignition switch will need to be cycled off and on when a new resistance is value is used. Compare readings on scan tool and gauge with values in OIL PRESSURE GAUGE VALUES  table. If values are approximately the same, go to next step. If values are not even close, go to step  12 .
   OIL PRESSURE GAUGE VALUES
   
   

   Resistance Value (Ohms)(1)	Actual Gauge Reading (PSI)
   200	80
   184	70
   168	60
   151	50
   99	40
   48	30
   37	20
   27	10
   16	0
   (1) Approximate resistance value.

8. Replace engine oil pressure switch. Recheck system operation.
9. Ensure oil pressure gauge switch is installed properly. Check for intermittent operation of oil pressure gauge switch. Remove oil pressure gauge switch. Use DVOM and measure resistance between terminal No. 1 of switch and threaded base of switch. Tap on switch and move switch around while watching DVOM readings. If reading drops to 5 ohms or less, go to step  8 . If reading does not drop to less than 5 ohms, go to step  14 .
10. With cluster removed and gauge cluster connector disconnected, use DVOM to check for continuity between ground and oil pressure gauge switch connector C2 terminal No. 1 and gauge cluster connector terminal No. 26 (Blue/Yellow wire). See Fig 1 . If any resistance value is indicated, go to step  14 . If no resistance is indicated, go to step  13 .
11. Locate and repair open in Blue/Yellow wire between gauge cluster and oil pressure gauge switch. Go to SYSTEM CHECK  .
12. Replace gauge cluster. See INSTRUMENT CLUSTER GAUGES  under REMOVAL & INSTALLATION. Go to SYSTEM CHECK  .
13. Problem may be intermittent. Pull on wires, shake harness and wiggle connectors. If problem is found, repair circuit and recheck operation. Go to SYSTEM CHECK  .
14. Locate and repair short to ground in Blue/Yellow wire between gauge cluster and oil pressure gauge switch. Go to SYSTEM CHECK  .

Fig 1: Identifying Gauge Cluster Connector Terminals

Courtesy of GENERAL MOTORS CORP.