One of the benefits of modern computer-controlled engines is efficiency. These kinds of engines manage the ignition and fueling in a precise manner so that very little fuel wastage occurs.
Take, for instance, fuel mixtures. In carbureted engines, fuel mixtures were handled by screws that let in either more or less air based on the direction that you turn the screw. Let in more air and less fuel, and the mixture becomes leaner. Let in less air and more fuel, and the mixture is richer. And once it’s set, that’s it—there’s no way to adjust it for different temperatures, fuel grade, or any other factors that can affect fuel mixtures.
Today’s computer-controlled engines adjust fueling automatically and on the fly. This is done through the oxygen (O2) sensor. The O2 sensor reads the exhaust in real time to determine the air-fuel ratio. It then sends the data to the computer, and the computer adjusts the mixture accordingly by controlling the fuel injectors.
Driving with a faulty O2 sensor means the computer won’t be getting the correct reading of the mixture and hence it won’t be able to adjust the air-fuel mixture properly. But if your engine starts and runs, and can stay running, it’s drivable. The only problem will be that your vehicle will run sluggishly or roughly, or it will stall. The default, limp-home fuel setting of an engine computer unit that receives no signal from the O2 sensor is an overly rich mixture. This is the safest setting to avoid detonation and burning a valve or piston due to an overly lean mixture. As a result, the engine will be less efficient and consume more fuel because of the overly rich mixture.
The worst thing that could happen is that the overly rich mixture could clog up the catalytic converter. The extra fuel that’s dumped into the cylinders will have to be burned off in the catalytic converter. The excess fuel will cause the converter to increase its operating temperature, which drastically shortens its lifespan. The ceramic core of the converter could melt if it reaches a high-enough temperature, which could cause a restriction and eventually clog the exhaust.
A new O2 sensor is about 10% to 20% the cost of a new catalytic converter. Thus, it is best if you change a faulty one immediately.
In summary, yes, you can drive with a faulty O2 sensor. But you’ll want to change it immediately, because otherwise, you’ll be spending more money on fuel and you risk having to spend more on a new catalytic converter as well.