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

Oxygen Sensor Wiring Diagram

03:30 Minutes Read

Oxygen sensor also called O2 Sensor or lambda sensor (λ) is an electronic sensor that measures how many oxygen molecules are present in the exhaust gas, which helps the ECU monitor the engine performance.

In this powerful guide, you will learn the wiring diagram of oxygen sensors such as 1, 2, 3, and 4 wire o2 sensor wiring diagrams.

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O2/Oxygen Sensor Wiring Diagram

Oxygen Sensor Wiring Diagram
Oxygen Sensor Wiring Diagram

The wiring diagram of the oxygen sensor is different based on year, make, and model. It depends upon the manufacturer, how they design the wiring diagram of the oxygen sensor. But, in this guide, I am more general than specific. I mean, I am giving you a general idea of how the oxygen sensor wiring is designed.

For your specific make and model, you should visit your car’s owner manual. The color of wires will vary and are color-coded depending upon the brand of the sensor.

Heated Oxygen Sensor Wiring Diagram

The oxygen sensor does not provide signal voltage to the car computer until gets hot, that’s why a heater is used to heat up the oxygen sensor. Most cars equipped with OBD II has heated oxygen sensor.

Oxygen sensor equipped with heater has an internal heater circuit that quickly heats the sensor to the operating temperature. This heater has a separate wiring circuit, which usually has two wires.

Oxygen sensors equipped with heaters mostly have 3 or 4 wires. Below are the three and four-wire heated oxygen sensor wiring diagrams.

  • 3 Wire Oxygen Sensor Wiring Diagram
  • 4 Wire Oxygen Sensor Wiring Diagram

3 Wire O2 Sensor Wiring Diagram

3 Wire Oxygen Sensor Wiring Diagram
3 Wire Oxygen Sensor Wiring Diagram

A three-wire oxygen sensor has one wire for the sensing element, which goes to the Powertrain Control Module (PCM). This wire is a voltage signal wire means the voltage produced by the sensor will send to the car computer.

The remaining two wires are for the heater, in which one wire goes to the fuse and relay in the fuse box and the second wire is earthed somewhere to the chassis. A three-wire oxygen sensor’s sensing element is earthed via a metal body to the exhaust manifold pipe.

4 Wire O2 Sensor Wiring Diagram

4 Wire Oxygen Sensor Wiring Diagram
4 Wire Oxygen Sensor Wiring Diagram

A 4 wire oxygen sensor wiring diagram is also called a universal O2 sensor wiring diagram. A four-wired oxygen sensor has four wires, two wires for the heater circuit and two wires are for the sensing element.

The sensing element wires go to the PCM, in which one wire is signal ground and the second wire is signal voltage. Here signal means the oxygen sensor sends the signals (voltage) to the Powertrain Control Module (PCM).

The remaining two wires are for the heater circuit, which is hot and earth. The heater circuit earth wire is grounded somewhere to the chassis of the car. While the heater circuit hot wire goes to the fuse and relays in the fusebox. As you know that the sensor heaters consume a lot of currents, so battery voltage is usually supplied through a relay and a fuse.

Here you should remember, the heater circuit of the oxygen sensor is controlled by the PCM or ECM through three different methods depending upon the car manufacturer. The oxygen sensor heater circuit is controlled by power (Hot wire), ground, or relay.

In some cars, the heater circuit’s earth wire is controlled by the PCM means the earth wire goes to the PCM. And some car manufacture controls the heater circuit by power means the hot wire goes to the PCM.

In some cars, the heater circuit is controlled by the relay in which relay is controlled by the PCM means the relay’s earth wire goes to the PCM. The essence of controlling the heater circuit by the PCM or ECU is, to know the open or short circuit of the heater circuit by taking the feedback.

This is an Info
In Most cars, the heater’s circuit is turned off by the PCM when the switch is ON and the engine is OFF to prolong the life of the sensor. And also in some cars, the heater circuit is disabled when it has an OBD II code.

This is an Info
A four-wire oxygen sensor is better than a three-wire oxygen sensor because a four-wire oxygen sensor has a dedicated ground wire, rather than relying on the exhaust manifold as a ground.


Non-Heated Oxygen Sensor Wiring Diagram

When the car has started, the oxygen sensor does not produce voltage until it gets hot. Non-heated oxygen sensors rely on exhaust gases to bring them to the operating temperature.

Sensor without heater core usually has one or two wires, which go to the ECU. Below are the one and two-wire non-heated oxygen sensor wiring diagrams.

  • One Wire Oxygen Sensor
  • Two-Wire Oxygen Sensor

One Wire Oxygen Sensor Wiring Diagram

One Wire Oxygen Sensor Wiring Diagram
One Wire Oxygen Sensor Wiring Diagram

A one-wire oxygen sensor has one signal wire means a voltage wire, which goes to the car computer. These kinds of sensors are earthed via the sensor’s metal body to the exhaust manifold pipe.

2 Wire O2 Sensor Wiring Diagram

2 Wire Oxygen Sensor Wiring Diagram
2 Wire Oxygen Sensor Wiring Diagram

A two-wire oxygen sensor has two wires, signal voltage, and earth. The voltage signal wire goes to the car computer. It is the wire through which the oxygen sensor sends the voltage to the computer. And the second wire is the earth, which also goes to the car computer (PCM).


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