How to Test O2 Sensors
Oxygen sensors are an integral part of the engine of today's cars. Not only do oxygen sensors help with gas mileage and the overall performance of the car, but they also decrease pollution and conserve fuel by making your car run as efficiently as possible. Oxygen sensors read the amount of oxygen in your exhaust to determine if your engine is running rich, lean, or efficiently. Sometimes if a car is not running correctly, faulty oxygen sensors are to blame. However troubleshooting car trouble can be difficult. With access to some fairly low-tech equipment, you can test your oxygen sensors to determine whether or not they are what is causing your car trouble.
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Instructions
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1
Remove the oxygen sensor from the engine. Locate the oxygen sensor on the exhaust manifold and unplug the wiring harness.
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2
Use the appropriate sized socket for the ratchet to remove the oxygen sensor by unscrewing it from the manifold.
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3
Mount the oxygen sensor in the vise and then connect the negative voltmeter lead to the case of the sensor and the positive lead to the sensor output wire.
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4
Light the propane torch and heat the fluted or perforated area of the sensor. Voltage should shoot up to 0.6 or higher within 20 seconds of heating. If you see the increase in voltage, remove the flame and watch for a drop to under 0.1 seconds. If you do not see the fluctuation in voltage, the sensor is probably fouled. If the sensor is displaying the differences in voltage, move on to step 3.
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5
Heat the perforated section of the sensor for two full minutes and watch for drops in voltage. Sometimes the connections will open up under heat and act the same as a loose wire. If the sensor fails this "two minute test" then it needs replaced. However, if it does not have sharp fluctuations in voltage under constant heat and it shows a difference in voltage with the addition/removal of heat, then the sensor is fine and can be remounted in the engine by reversing Step 1.
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Tips & Warnings
Digital voltmeters are the best way to test O2 meters as they can register a very low voltage and do not detract voltage due to a low volume current. Do not use non-powered analog style voltmeters.
Make sure the engine is cooled down before removing the oxygen sensor.
