How To Test A 4 Wire O2 Sensor With A Multimeter

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The oxygen sensor also called the O2 sensor or lambda sensor of the car records the amount of oxygen content in the exhaust and reports it to the ECU of the car. This information is then utilized to optimize the air-fuel ratio in the combustion chamber.

The oxygen sensor can get corroded and need a test to verify the proper functioning of the oxygen sensor. In this powerful guide, you will quickly learn how to test the oxygen sensor with 4 wires.

How To Test A 4 Wire O2 Sensor With A Multimeter

How To Test Oxygen Sensor
How To Test Oxygen Sensor

The oxygen sensors could have any number of wires ranging from one wire to four wires. The oxygen sensors with 1 or 2 wires are non-heated whereas the oxygen sensors with 3 or 4 wires are heated oxygen sensors.

The oxygen sensor with 4 wires is the most commonly used oxygen sensor. Two wires are for the heated circuit and the other two wires are for sensing elements. They work by producing their very own voltage by getting hot.

A zirconium bulb is placed on the tip of the oxygen sensor sitting in the exhaust. The bulb is coated with platinum inside out acting as its electrodes.

The inside of this bulb is vented and the outside is exposed to hot gases in the exhaust. The voltage is caused by the difference in oxygen level between the bulb and the atmosphere.

If the air-fuel ratio is lean, the voltage generated would be low around 0.1 volts whereas if the air-fuel ratio is rich, the voltage generated would be high around 0.9 volts.

1. Oxygen Sensor’s Heater Wires Test

Oxygen Sensor’s Heater Wires Test
Oxygen Sensor’s Heater Wires Test

First of all, we check the oxygen sensor’s heater wires to check if the heating wires are broken. You can check this by the following method:

  • Switch the Digital Multimeter to the Ohmmeter mode.
  • Back probe the oxygen sensor heater’s hot and ground wire.
  • Connect the red lead of the multimeter to the heater hot wire.
  • Connect the black lead of the multimeter to the heater ground wire.
  • If the heater wires of the Oxygen Sensor of the car are functioning correctly the readings on the Digital Multimeter should assume some value between 10 Ohms to 20 Ohms.

This test should be carried out when the engine of the car is switched off.

2. Oxygen Sensor’s Signal Wires Test

Oxygen Sensor's Signal Wires Test
Oxygen Sensor’s Signal Wires Test
  • Ensure that the engine of the car is cooled.
  • Switch the Digital MultiMeter to the voltmeter settings.
  • Back probe the oxygen sensor’s signal voltage and ground wire.
  • Connect the black lead of the Digital MultiMeter to the back probed ground signal wire.
  • Connect the red lead of the Digital Multimeter to the signal voltage wire.
  • Turn the engine of the car on.
  • The voltmeter should show you the reading somewhere around 0.1 to 0.9 volts if the sensor wires of your car are working properly.

If you don’t get readings similar to those shown above, you must get your car’s oxygen sensor diagnosed and repaired or replaced by a mechanic immediately as it is very vital for the correct air-fuel ratio in the combustion chamber of the car.

FAQs

What happens if you use the wrong O2 sensor?

If you use the wrong O2 sensor, it can cause your car to run lean or rich. Lean means that there is not enough fuel being delivered to the engine, and rich means that too much fuel is being delivered. Either way, using the wrong O2 sensor can lead to engine damage.

Is there a fuse for the oxygen sensor?

The oxygen sensor is equipped with a fuse for the heater circuit. If the fuse is blown, the heater will not heat up the sensor and the sensor will not be able to properly measure the oxygen content of the exhaust gases.

Related • Oxygen Sensor: 1, 2, 3, 4 Wire O2 Sensor Wiring Diagram

What Is Oxygen Sensor In A Car, How It Works, & Construction

Where Is The Oxygen Sensor Located: Locate O2 Sensor Easily

What Are Bank 1 And Bank 2: (O2 Sensor 1 & 2) Locate Easily

Learn 9 Horrible Symptoms Of Bad Oxygen Sensor

What Causes An Oxygen Sensor To Fail: Know 7 Reasons


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