O2 sensor testing tool

Connect the red probe to the o2 sensor signal wire. The black probe should be connected to the ground. Start the car and then check the voltage readings on the voltmeter. The voltage readings of the o2 sensor should vary between mV and mV 0. The o2 sensor should be operating in a normal manner and you can stop testing if it falls outside this range.

If it is outside of this range, the engine is probably not working properly loose hose , or the o2 sensor may be defective. Continue with the next steps if it is not within range. The positive crankcase ventilation valve PVC , located on the valve cover, must be disconnected from the hose. This will allow for more air to enter the engine.

The voltmeter should read approximately mV 0. To test the response of the o2 sensor to high fuel consumption, reconnect the PVC line.

This will allow you to disconnect the plastic connection from the air cleaner assembly. To reduce the air entering the engine, block the hose connection opening using a rag. The voltmeter should be checked. Due to the reduced oxygen entering the engine, it should read mV 0. Likely, the o2 sensor is not responding in this manner.

Connect the hose to your air cleaner. The problem could be caused by another component if the o2 sensor responds correctly to the rich and lean fuel tests.

Potential issues include a vacuum leak, an ignition system, or something similar. If the o2 sensor does not respond correctly, it is likely that it is defective and should be replaced.

Bottom line After all, you need to test the sensor to determine if it is defective or if there is another problem. Related Posts. June 23, What do I do? January 5, Log in Forgot your password?

Start Prev 1 Next End. Usually I'll look at the front sensor on a scan tool to make sure, with a little rpms held, that it's oscillating from at least mv to mv. You can pull a vacuum line off and see if immediately drops down to low voltage and introduce propane into the intake to see if voltage rises. You won't really be able to judge the speed of these events on a scan tool, but these tests will give you a good idea of the sensor is responding to changes in the mixture.

Paul has some great videos out there on o2 sensor testing for you to check out. The changes move the voltage in the opposite direction though, and voltage doesn't oscillate, it just sees a change in mixture and more quickly goes back to it's base value.

Tyler has a sticky in the diagnostic tools and techniques forum section on testing these sensors. Nissan Tech. I think Andy calls it a 'dipsy doodle'? I can't remember exactly. The sensor voltage should cycle or fluctuate within the mV mV 0. This means the sensor is operating properly. If the O2 sensor only produces a low- or high-voltage signal, either you have an engine performance issue or the oxygen sensor stopped working.

To verify sensor operation, conduct the next two tests. If the oxygen sensor in your vehicle responded correctly to your tests, you might have a problem with another component affecting fuel efficiency. The engine may have a vacuum leak, a problem in the ignition system or something similar. Replace the oxygen sensor at the recommended manufacturer interval for better engine performance. Once you know how to check an oxygen sensor, you can verify whether the unit is actually working or in need of replacement.

These tests will save you money and time—and help you fix your vehicle sooner. Also, you might want to check the service interval for your O2 sensor in your repair manual. As driving miles accumulate, exhaust byproducts cover the tip of the unit that protects the sensing element. Then the sensor efficiency drops, causing engine performance issues. Eventually, the sensor stops working. So it's a good idea to replace it at the recommended schedule to restore fuel efficiency and reduce emissions.

Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Answer: The rear sensor monitors the catalityc converter job. The downstream O2 sensor fluctuates very little if the cat is working properly. Voltage reading probably an average of 0. Answer: It is possible. The oxygen sensor located downstream from the catalytic converter is usually the one that makes the ECU throw this code. This O2 is a cat monitor, and when the computer senses the catalytic is not doing its job based on the feedback from this sensor, it lights the CEL.

However, other faults can make this code appear, like an exhaust leak, a bad O2, a misfire or a leaking fuel injector. Answer: The average for that sensor is 0. It constantly fluctuates between 0.

Question: If one of the four oxygen sensors is bad, will that cause the bad sensor to throw codes for all of them? Or does multiple oxygen sensor malfunction sound more like a ground wire issue? Answer: Use a sensor adapter. As long as the head of the O2 remains in the stream, it'll work. Answer: The front sensor should be constantly fluctuating between near 0. Question: My 8. I turn the key off, it starts right up and runs great for a while before quitting.

What could be the problem? Answer: If the sensor is worn but still within the working parameters, it won't trigger a trouble code. Question: My O2 sensor is reading 0. There aren't any error codes.

The engine is a 1. Answer: It seems like a vacuum leak. Check for leaks using carburetor cleaner. They are hard to find sometimes. A smoke test, if necessary. Question: Can I test the voltage on a downstream air sensor in the exhaust while unplugged? Like pulling it out and using a torch idea? Answer: Yes. The heat from the propane torch eliminates the oxygen from around the sensor, which causes the sensor to send a voltage signal.

Question: On my scanner, the oxygen sensor reads a fixed 1. Can a sensor reach 1. Is the sensor broken? Answer: A titania oxygen sensor can read up to 1. Check the type of system your vehicle uses first and operating parameters. You may find this information in your vehicle repair manual.

It may also tell you how to test the sensor. Answer: The master cylinder might be leaking and fluid entering the brake booster. Applying the brakes can send the fluid into the engine, having that extra boos effect in rpms. Question: Every source says to "backprobe" an O2 sensor. The O2 sensor is a bimetallic junction that produces a voltage when heat is applied. And I did just measure a voltage with the sensor disconnected from the harness and measuring only the sensor's signal wire and ground, engine running.

So, is there a valid test protocol doing it this way? Answer: Actually, the recommended tests make use of a scope or scan tool, while monitoring sensor switching response time while idling, and load conditions.

I haven't heard of a specific protocol to use while the sensor is unplugged though.