An 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.
An oxygen sensor is a device in a car that helps to monitor the levels of oxygen in the exhaust system. By doing this, it helps the engine to run more efficiently and produce fewer emissions. The oxygen sensor is located in the exhaust system.
An oxygen sensor wiring diagram is a drawing that shows how the oxygen sensor is connected to the vehicle’s electrical system. The diagram will show the location of the oxygen sensor, the type of sensor, and the color of the wires. The diagram may also show the location of other sensors and components that are related to the oxygen sensor.
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
The wiring diagram of the oxygen sensor is different based on year, make, and model. It depends upon the manufacturer how they design the oxygen sensor wiring diagram. 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 owner’s manual. The color of wires will vary and are color-coded depending upon the brand of the sensor.
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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.
The oxygen sensor equipped with a 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
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3 Wire O2 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 relays in the fuse box and the second wire is earthed somewhere in 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
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 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 in the chassis of the car. While the heater circuit’s hot wire goes to the fuse and relays in the fusebox. As you know that 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 (Hotwire), 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 manufacturers control the heater circuit by power means the hot wire goes to the PCM.
In some cars, the heater circuit is controlled by the relay whereas the 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.
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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.
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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.
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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
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.
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2 Wire O2 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).
Frequently Asked Questions (FAQs)
The wiring color of the oxygen sensor depends upon the make and model. Make and model will dictate which wires are used for what purpose. Usually, the white wires on an oxygen sensor are for the heater. The heater is not powered on all the time, but only when the temperature is too low for the sensor to function properly. The reason for this is that the oxygen sensor measures the amount of oxygen in the exhaust gas. If there is too little oxygen, it means that the fuel mixture is too rich and needs to be adjusted.
If you unplug your O2 sensor, it will no longer be able to measure the oxygen content of the exhaust gas. This can cause the engine to run too lean or too rich, depending on the situation. If the engine runs too lean, it may not have enough power and may overheat. If the engine runs too rich, it will use more fuel than necessary and may produce excessive emissions.
Technically, the car is still drivable without an oxygen sensor, but it will not run as efficiently as it could. Without it, the car will run rough and sluggish. Cars are designed to run on a mixture of air and fuel, with the ideal ratio being 14.7 parts air to 1 part fuel. The oxygen sensor is responsible for monitoring the level of oxygen in the exhaust gases and adjusts the air-fuel mixture accordingly. Without an oxygen sensor, the car will still run, but the engine will be less efficient and the car will likely experience more wear and tear.
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