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How to replace the oxygen sensor in your car

How to replace the oxygen sensor in your car

Old cars were tuned by man with dirty fingernails, hammers, screwdrivers and usually some swearing. They were fine-tuned by driving, by smell and by noise. Today’s generation doesn’t understand all that. In fact, given the sudden increase in ‘wrong fuel recovery’ stories, they can barely put the right sort of liquid dinosaur in their cars, but we digress.

The point is that modern cars have brains, and they do all the thinking for us. A case I point would be air/fuel mix. This is a vital part of a happily running engine, as the right mix is dependent on temperature, altitude and other atmospheric conditions. Back in the day, you’d wind a screw into or out of your carb.

In a modern car, the brain does it all for you. But only if it’s getting the right signals from the sensor. If this is broken, you’re in trouble. Which is why we’ve made this guide on how to change it.

01 Jack it up

01 Jack it up

The sensor is under your car, so you’re going to need to jack it up. Make sure you follow our guide on safe ways to get your car in the air, we don’t want you to go and hurt yourselves!

02 Keep it cool

02 Keep it cool

The sensor monitors spent exhaust gases to determine the air/fuel mix before sending the signals back to the car’s brain. This of course means it’s mounted in the exhaust pipe, so on that basis, you need to make sure it’s cool before you start working on it, otherwise you’ll burn your fingers.

03 Unplug then undo

03 Unplug then undo

The sensor will be connected to the car’s loom via a plug towards the front of the car. This may be mounted either inside the car via a hole in the floor, outside the car. Unplug the connection first, then use a spanner to loosen the sensor. If you leave it plugged in, you’ll bind up the wires.

04 Clean your bunghole!

04 Clean your bunghole!

That sounds somewhat ruder than we anticipated. But still, you need to clean the threaded hole in the exhaust with a wire brush before fitting the new part. Get into the thread to make sure there is no debris there, otherwise you won’t get an airtight seal.

05 Now go back

05 Now go back

Now, with the new oxygen sensor, work your way back through the above steps to fit it. If the connecting cable dangles too low, be sure to cable tie it up and away from the exhaust. Also, check the manufacturer settings for any steps you may need to take to sync the plug to your car.

Many will simply recognise the part as new and carry on, others may need specific setup. Your Haynes Manual will guide you.

About the author

Chris Pollitt is an award-winning automotive word-wrangler, editor of the website Not 2 Grand and a keen collector of crappy old cars.

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