Check Gauges Lamp: Testing and Inspection

LOW OIL PRESSURE WARMING LAMP/CHECK GAGES TEST








The oil pressure/check gage warning lamp will illuminate under any of the following conditions:

1. Lamp check when the ignition key is turned to the ON position for about two seconds.

2. The oil pressure switch is closed to ground The switch grounds the lamp and is in put to the body controller which turns on the lamp over the bus.




3. Oil pressure sending unit is high resistance, low pressure. The body controller will turn on lamp over the bus. The lamp also illuminates when the engine oil pressure drops below a safe oil pressure level.

To test the system, turn the ignition key to the ON position. If the lamp fails to light, during the two second lamp, inspect for a burned out lamp or disconnected socket in the cluster.

CONDITION: WARNING LAMP DOES NOT LIGHT

If the lamp goes out after the lamp check, inspect the connection to the oil pressure switch and sensor. Check that the wires are going to the correct terminals of the sending unit. Both the switch and sensor must fail to result in the light going out. If the connector and wiring are OK, use the DRB II to read the oil pressure switch at the body controller. Disconnect the sending unit connector. Using an jumper wire, connect one end to the switch terminal and the other to ground. If the lamp fails to light check for continuity to the cluster and body controller from the pressure switch. Check for short from pressure sensor circuit to ground. Check the wiring go to the body controller connector for proper terminals.

CONDITION: LAMP STAYS ON WITH ENGINE RUNNING

If the light stays on with engine running, perform the combination sending unit tests. If the sending unit is OK perform the following:

1. Using a DRB II monitor the oil pressure switch with the sending unit connector disconnected. The switch should read open. If it does not, there is a short in the wiring. Repair as necessary. The circuit goes from the switch to the body controller and the cluster.

2. Connect the sending unit. Start the engine. Using the DRB II, read the oil pressure level. If the DRB II reads ignition voltage, there is a open circuit in the sensor wiring circuit. Repair open circuit.

COMBINATION OIL SENDING UNIT TESTS








The combination oil unit has two functions:

1. The normally closed circuit keeps the oil pressure warning lamp on until there is oil pressure.

2. The sending unit provides a resistance that varies with oil pressure.

3. To test the normally closed oil lamp circuit, disconnect the locking connector and measure the resistance between the switch terminal and the metal housing. The ohmmeter should read zero ohms.

4. Start the engine. If there is oil pressure, the ohmmeter should read an open circuit.

5. To test the sending unit, measure the resistance between the sending unit terminal and the metal housing. The ohmmeter should read open.

6. Start the engine. The ohmmeter should read between 30 and 55 ohms, depending on engine speed, oil temperature, and oil viscosity.

7. If the switch and sensor read low pressure with the engine running, remove the sending unit. Connect a pressure gauge in place of the sending unit to test pressure. For oil pressure specifications, refer to Group 9, Engine. If OK, go to step 8.

8. If the above results are not obtained, replace the switch.