Comprehensive Guide to Testing Oil Pressure Sensors

What Tools and Devices are Needed to Test Oil Pressure Sensors?

To test oil pressure sensors, you will need the following tools and devices:

Multimeter: Set to Ohms for continuity and resistance measurements.
Compressed Air: For simulating oil pressure, if testing the sensor off the vehicle.
Oil Pressure Gauge: Optional, for verifying the actual oil pressure.
Wire Connectors and Leads: For connecting the multimeter to the sensor.

Identify Sensor Type:
Determine if the sensor is normally open or normally closed. Normally closed sensors are more common, where the contacts are closed when there is no oil pressure and open when the pressure exceeds a set threshold.
Engine Off Test:
Unplug the electrical connector from the oil pressure sensor.
Set the multimeter to Ohms and measure the resistance between the terminal and the body of the sensor. For a normally closed sensor, this should show a low resistance (near zero Ohms) indicating a closed circuit.
Engine Running Test:
Start the engine and let it run until the oil pressure stabilizes.
Measure the resistance again. For a normally closed sensor, the contacts should open, and the multimeter should display infinity or a very high resistance.
Bench Testing:
If possible, remove the sensor and use compressed air to simulate oil pressure. Apply air pressure within the specified range (e.g., 0.2 to 0.5 bar) and measure the resistance. The contacts should open when the pressure is applied.
Additional Checks:
Verify that the sensor is properly grounded by measuring resistance from the signal terminal to any part of the engine block or heads. The values should match to ensure there is no electrical resistance through the mounting threads.

Warning Light: The oil pressure warning light on the dashboard may illuminate continuously or intermittently.
Incorrect Readings: The oil pressure gauge may show incorrect or erratic readings.
Engine Performance Issues: Low oil pressure can lead to engine noise, overheating, or reduced performance.
Oil Leaks: Physical signs of oil leaks around the sensor or engine.

Infinity or High Resistance: If the multimeter shows infinity or very high resistance when the engine is off and the sensor is normally closed, it indicates an open circuit and potential failure.
No Change in Resistance: If the resistance does not change when the engine is running and oil pressure is applied, it suggests the sensor is faulty.
Physical Inspection: Look for signs of oil leaks or physical damage to the sensor.

Engine Damage: Driving with low oil pressure can cause severe engine damage, including bearing failure and increased wear on moving parts.
Reduced Engine Performance: Low oil pressure can lead to decreased engine performance, increased fuel consumption, and potential engine failure.
Safety Risks: Ignoring oil pressure warnings can result in engine failure while driving, posing safety risks.

Immediate Inspection: If the oil pressure warning light comes on, stop the vehicle as soon as it is safe to do so and check the oil level.
Sensor Replacement: If the sensor is found to be faulty, replace it with a new one that matches the specifications of the original sensor.
Oil Pressure Check: Use an oil pressure gauge to verify the actual oil pressure and ensure it is within the recommended range.

Check Electrical Connections:
Ensure all connections to the sensor are secure and not damaged.
Verify that the wiring harness is intact and not shorted.
Sensor Calibration:
Some sensors may require calibration. Refer to the vehicle’s repair manual for specific procedures.
Bench Testing:
Use compressed air to simulate oil pressure and test the sensor off the vehicle. This can help isolate the problem.

Electrical Failures: Corrosion or damage to the electrical connections can cause the sensor to malfunction.
Mechanical Failures: Physical damage to the sensor or its mounting can prevent it from functioning correctly.
Oil Leaks: Oil leaks around the sensor can cause it to fail prematurely.

Free ASE Study Guides: “Oil Pressure Switch Diagnosis and Testing” – This guide provides detailed steps for diagnosing and testing oil pressure switches, including continuity checks and bench testing.
iRV2 Forums: “Testing Oil Pressure Gauge and Sending Unit” – This forum discussion includes practical advice and troubleshooting steps for testing oil pressure gauges and sending units.
YouTube – Royalty Auto Service: “How to test an oil pressure switch – with tutorial” – This video tutorial demonstrates how to test an oil pressure switch using a multimeter and compressed air, explaining the principles of operation and common failure scenarios.