Engine Oil Pressure Gauge Inaccurate/Inoperative

Perform INSTRUMENT CLUSTER DIAGNOSTIC SYSTEM CHECK under TROUBLE SHOOTING. Go to next step.
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 3.0L V6 - VIN [R] article in ENGINES section.
If oil pressure gauge is working but inaccurate, go to step 7). If gauge reads properly, go to next step.
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).
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).
Remove instrument cluster from instrument panel. See 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).

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

184

168

151

⁽¹⁾	Approximate resistance value.

Replace engine oil pressure switch. Recheck system operation.
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).
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).
Repair open in Blue/Yellow wire between gauge cluster and oil pressure gauge switch. See INSTRUMENT CLUSTER DIAGNOSTIC SYSTEM CHECK .
Replace gauge cluster. See INSTRUMENT CLUSTER GAUGES under REMOVAL & INSTALLATION. Go to INSTRUMENT CLUSTER DIAGNOSTIC SYSTEM CHECK .
Problem may be intermittent. Pull on wires, shake harness and wiggle connectors. If problem is found, repair circuit and recheck operation. Go to INSTRUMENT CLUSTER DIAGNOSTIC SYSTEM CHECK .
Locate and repair short to ground in Blue/Yellow wire between gauge cluster and oil pressure gauge switch. Go to procedures in INSTRUMENT CLUSTER DIAGNOSTIC SYSTEM CHECK .

Fig 1: Identifying Gauge Cluster Connector Terminals
Courtesy of GENERAL MOTORS CORP.