How to replace an oxygen sensor

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View of an oxygen sensor, attached to an exhaust system.

The common location for an oxygen sensor. (Photo Credit: CC BY/Ernesto Andrade/Flickr)

Have you been staring at that check engine light for months? Bust out your OBD-II scanner, and you’re likely to find that you have a failed oxygen sensor. Luckily, an O2 sensor isn’t difficult to swap out. He’s how to replace an oxygen sensor with minimal work.

The oxygen sensor’s job

A car’s oxygen sensor sends data to the vehicle’s computer system to help determine how the catalytic converter will work and how much fuel to inject into the mix. This is critical to proper engine function.

Replacing an oxygen sensor with the same type installed by the manufacturer can be somewhat expensive. However, cheaper alternatives like universal replacement sensors from your local auto parts store are available. For older vehicles, a basic unit with a single wire that is grounded to the exhaust pipe is common. With more recently made cars, you’ll need a heated O2 sensor with as many as four wires. To be certain about what you’ll need, removing the oxygen sensor and bringing it to the store is helpful.

How to remove the oxygen sensor

As the oxygen sensor is tightly attached to the exhaust system, some penetrating oil on the threads of the sensor will make it easier to loosen. Detach the wiring harness – don’t cut it – then use an O2 sensor socket from an auto parts store to remove the old sensor from the socket. If it’s difficult to move, try more oil or do the job with the engine warm. (Use gloves to protect against burns).

You shouldn’t cut the wires off because many types of oxygen sensors need the wires to “breathe,” according to Popular Mechanics. The O2 sensor compares exhaust air to outside air, sending the readings as voltage to the car’s computer. Cutting the wires and soldering them later clogs the transmission path, negating the sensor.

There are always exceptions, however. Some oxygen sensors sample air at the base of the unit and have bare wires. In this case, you must cut the plug off the old sensor and splice it to the replacement sensor. Use heat-shrink tubing over the wires, solder and apply heat to seal the joint.

Handling oxygen sensors

Be careful – oxygen sensors are fragile. Don’t allow the tip to touch anything. Apply anti-seize so that it’s easy to rethread, and use your O2 sensor socket to put the new sensor in. Reroute the wire and attach the wire connector, making sure the wire does not make direct contact with the exhaust system.

How to replace an oxygen sensor




Popular Mechanics

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