How to Test 02 Sensors

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What is an O2 Sensor?

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An 02 sensor is an oxygen sensor and it measures how much unburned oxygen is in the exhaust as the exhaust exits the engine. The 02 sensor lets the computer inside the car know if there is not enough oxygen in the exhaust, or too much exhaust. This little sensor regulates your vehicle and ultimately makes it safe to drive. Driving with a faulty 02 sensor can lead to expensive repairs to your vehicle. 

In this blog, we will discuss the details about 02 sensors and explain how you will be able to test your 02 sensor by yourself. This process is not as difficult as it sounds, and after a few tries, you will be able to test your 02 sensor

How Does an O2 Sensor Work?

The sensor is basically a miniature generator. It produces its own voltage when it gets hot. At the end of the sensor, there is a ceramic bulb that is coated in a layer of platinum. Inside the bulb, there are two strips of platinum that act as electrodes, which makes the entire sensor work. 

The outside of this bulb is exposed to hot gasses that are present in the exhaust when you are driving. When the air steeps into the sensor, there is a difference in the oxygen levels between the exhaust and the outside air, which is what causes voltage to flow through the bulb. The greater the difference, the higher the voltage reading. 

Also Read: How Do You Test a Brake Master Cylinder?

Why it’s Important to Test an O2 Sensor

It is important to test an 02 sensor to ensure that it is working properly. If you have a faulty 02 sensor and continue to drive around with it, you will only cause more damage to your vehicle. It is vital to know how to test your 02 sensor so you can be confident that your vehicle is working properly. 

Signs that an O2 Sensor is Failing

There are several obvious signs that indicate your 02 sensor is failing. These signs include:

  • Rough engine idle and misfires
  • Check Engine light is on
  • Bad gas mileage
  • Rotten egg smell

It is important that you test your 02 sensor after noticing these signs. You should never ignore a sign from your vehicle that something is wrong. 

Also Read: How to Test 3 Wire Crank Sensor With Multimeter

Things You’ll Need to Test an O2 Sensor

You will need a 10-megaohm impedance digital voltmeter for testing the o2 sensor. You should set it to the millivolt (mV) DC scale. 

A Step by Step Guide on How to Test an O2 Sensor

Testing your 02 sensor will be easier if you know exactly what to do. Here is a step-by-step guide. 

Step 1: Prepare all the tools you’ll be needing. Get your tools out and ready to begin the process. Make sure you have everything you need before you get started. 

Step 2: Visually inspect the wires of your 02 sensor 

Step 3: Connect the backprobe to the oxygen sensor’s signal wire.

Step 4: Connect the positive lead from the digital voltmeter to the backprobe.

Step 5: Connect the negative lead from the digital voltmeter to a good solid ground point on the chassis of the vehicle.

Step 6: Turn the vehicle back on and check the reading on the voltmeter. The reading should fluctuate rapidly.

Step 7: Create a vacuum leak to ensure that the O2 sensor responds properly to a lean air-fuel mixture.

Step 8: If your vehicle does not have a vacuum port or if creating a vacuum leak causes the vehicle to stall, you can perform a propane enrichment test.

If during steps 8 to 10 the voltage does not change or does not change in the expected manner, then the oxygen sensor is bad and should be replaced.

Also Read: How to Replace a Torque Converter Clutch Solenoid

Safety Guidelines When Testing an Oxygen Sensor

As you probably already know, working with vehicles can be a dangerous process. These machines are large and complicated, and parts of it can be quite flammable. When testing your 02 sensor, be very aware of any sudden changes. If a rotten smell enters the air, or your car begins to get very hot, turn the vehicle off and back away. While it comes in handy to know how to take care of your car, it is not worth the risk of injuring yourself or others or damaging the belongings that are around you. If you feel that you are taking a risk, call a mechanic and let him take care of the job 

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Final Thoughts 

Testing your 02 sensor will help you maintain a working vehicle and will ensure that you can drive your car safely. While the process may seem complicated at first, practice makes perfect, and once you test the sensor a few times, you will get the hang of it.

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