How to test an oxygen sensor with 2 wires and 4 wires.

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How to test the 2-wire oxygen sensor and for the 4-wire oxygen sensor. With your diagram and video.

How to test an oxygen sensor with 2 wires and 4 wires..

The tests are based on the following:

Physical sensor check:

Cables and the condition of the sensor connector must be checked. That they are not in poor condition, matches or anything else that suggests a problem of false contact or loss of electrical connection.


The sensor should not be hit, if it hits, the internal ceramic breaks and leaks and will stop working.

Electrical check:

In this case, it must be checked that there is no short circuit between the sensor and the housing or between the internal heating resistor (if it has the sensor).

For the two wire oxygen sensor it would be as shown below.

pronar sensor oxígeno de dos cables

This sensor has no heater.


For the 4-wire one that if it has a heating resistor would be:

probar sensor de oxígeno de 4 cables

To better focus on the meaning of the pins, below I leave the diagram of both oxygen sensors, both for 2-wire and 4-wire.

diagrama para probar sensor de oxígeno de 2 cables y 4 cables

After verifying that there are no short circuits, the sensor is operated:


Start the car and wait for the oxygen sensor to warm up. While it is not hot, you do not see tension in the sensor. It will only mark zero.

Once hot, it will start to oscillate between 0.1V and 0.9V. The frequency is in the order of 2 Hz or 3 Hz.

With the digital multimeter, you will see changes in reading that vary from 0.1V to 0.9V look as if it were random, but in reality you are measuring a sine-like wave.

With my measuring device if you will see the LEDs in reciprocating. Seeing exactly the measurement that is coming out of the sensor.


If there is no oscillation, we must rule out problems with other parts of the engine.

Accelerating the blow motor causes sudden rich mixing and the voltage shift towards 0.9V should be seen. After the acceleration it is noted that the voltage will go to 0.1 V quickly.

If the above occurs, then our sensor is responding to variations.


If the sensor keeps in a rich mixture (more than 0.8V) at all times, it may be due to dripping injectors.

If the sensor is kept in a poor mixture (less than 0.2V), it is possible that it has an improper air intake to the motor. You should check the brake booster hoses, vacuum hoses to the intake manifold that are not broken or loose.

¿Video of how I did it for the 2-wire one?

Do you have questions or doubts?

Questions or suggestions can use the form below and I will gladly answer them.

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Written by Dennis García.

Mechanical Girl


Todo muy bien.

Gracias Chica Mecanica.

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    How to test an oxygen sensor with 2 wires and 4 wires.

    How to test an oxygen sensor with 2 wires and 4 wires.

    How to test the 2-wire oxygen sensor and for the 4-wire oxygen sensor. With your diagram and video.

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    • Asked by Ariel Cabral
      on 01/20/2020
      Hola muchas bendiciones y gracias por tus aportes son geniales quería consultar sobre un Ford fiesta como identificar los cables del sensor de oxigeno es de 4 cable tengo solo los colores pero no tengo números identifique el positivo y el negativo de la resistencia pero como hago con los otros dos Answer:
      Que tal Ariel, con los otros dos, solo debes conectar el sensor al tubo de escape y lo dejas sin conexión electrica. Cuando el motor caliente, a los 10min. mides con un voltimetro los cables. Te dara menos de 1V entre esos dos terminales. Si conectas el voltimetro y te da negativo inviertes entonces la conexión del mismo para que te de positivo la tension. Entonces, donde conectaste el cable rojo del voltimetro es tu positivo del sensor y el cable negro es el negativo de sensor. Listo. Con el conector que viene de la computadora es el mismo procedimiento.
    • Asked by Armando
      on 01/28/2020
      Cuando mides si tiene corto, pones el multimetro en escala de continuidad? Y por que no pones unos de los terminales del multimetro a bsteria, sino que ambos los pegas del conector del sensor, saludos! Answer:
      Que tal Armando. Si tiene corto mide cero ohms en la resistencia. Si tiene un corto en el sensor de O2, deberia de medir algo de resistencia. Y no lo mido en ambos cables del O2 porque de hecho estoy buscando los cables, pero si ya los conoces puedes medir en los dos con el multimetro sin problemas.
    • Asked by Israel
      on 05/15/2020
      Hola hermosa tengo un scion tc y me dio el codigo P0031 lo cambie por un sensor boch universal pero no se quito la luz ..el arnes donde va conectado el sensor tiene que haber continuidad ? Grasias Answer:
      No, Alli no debe haber continuidad entre pines. Solo un valor de resistencia cuando el sensor tiene calefactor.

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