While it’s safe to drive with a broken oxygen sensor, it can significantly impact engine performance and fuel economy—and you won’t be able to pass emissions testing until you replace the part.

Will your car run with a bad oxygen sensor? In most cases, yes. But it’s not a good idea to operate a vehicle long-term without a working O2 sensor. In this article, our

car repair

experts take a closer look at how long you can go without replacing your faulty oxygen sensors.

Is it safe to drive with a broken O2 sensor?

Generally speaking, it’s safe to drive for a short time with a broken O2 sensor—but the longer you go without replacing it, the greater the risk of damage to expensive vehicle components like the catalytic converter and engine.

Your car’s O2 sensor is a vital part of the exhaust system. Most modern vehicles have two types of oxygen sensors: an upstream sensor that monitors the air-fuel mixture coming from the engine, and a downstream sensor placed after the catalytic converter to check the mixture again.

A broken upstream O2 sensor is a more serious problem than a downstream sensor. While the downstream sensor might be sending incorrect readings to the electronic control unit (ECU), those readings aren’t as likely to impact engine performance or endanger the catalytic converter. With a faulty upstream sensor, however, you’re more likely to see decreased engine performance, poor gas mileage, and even damage to the catalytic converter.

The bottom line? While driving with a faulty oxygen sensor won’t put you in immediate danger, it’s best to get it replaced within a few weeks or a few hundred miles—especially if it’s an upstream sensor.

MORE:

Oxygen sensor replacement cost estimate

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How long can you go without changing your O2 sensors?

In new vehicles, oxygen sensors are expected to last for about 7 – 10 years, or up to 100,000 miles. If your vehicle is older, you may need to replace the sensors as often as every 3 – 5 years.

If you’re already noticing the signs of a bad O2 sensor, it’s best to replace it as soon as you can. If you need to put off repairs for a few weeks (e.g. until your paycheck comes in), the car will still run—but delaying any longer could lead to more extensive damage.

MORE:

Why is there an exhaust smell in your car?

Can a bad O2 sensor cause engine damage?

In the long term, yes! Oxygen sensors are crucial to proper engine performance because they communicate with the engine computer in real time, allowing the computer to adjust the fuel injectors correctly. If the sensor doesn’t work, the air-to-fuel ratio in your car’s engine might not be correct, which can lead to excess fuel consumption and poor engine performance.

But the part you really need to worry about is your catalytic converter. A bad sensor can cause your catalytic converter to become clogged—and a catalytic converter replacement costs anywhere from $1,000 to $4,000 or more.

MORE:

How to unclog a catalytic converter

How to tell if your O2 sensor is broken

The biggest signs of a faulty O2 sensor are decreased fuel efficiency, poor engine performance, and a failed emissions test.

Keep your eye out for the following common symptoms of a broken oxygen sensor:

Flickering check engine light: If your

check engine light is on

—and especially if it goes on and off—the O2 sensor could be to blame.

Rough driving:

Engine misfiring

, stalling, rough idling, and even loss of power can all be a sign of a bad oxygen sensor.

Foul smells and black smoke: A telltale rotten egg smell is a classic sign of trouble with the emissions system, as is

dark or discolored exhaust gas

Poor fuel economy: A faulty oxygen sensor can throw off the lean mixture in your vehicle’s engine and lead to

excess fuel consumption

If you have an

OBD-II scanner

, you can use it to scan for

trouble codes

associated with the upstream and downstream oxygen sensors. A professional mechanic or auto parts store can also help you diagnose the problem if you notice any of these symptoms.

MORE:

What does engine code P2A04 mean?

How much does an oxygen sensor replacement cost?

Depending on the exact problem with your O2 sensor, your repair costs could range from $100 to $300, on average.

Swapping out your faulty sensor with a new sensor isn’t the cheapest repair, but it’s a lot more affordable than replacing the catalytic converter or engine.

MORE:

How to fix your catalytic converter without replacing it

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