WEBVTT - How does the oxygen sensor in a car work?

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<v Speaker 1>Welcome to brain Stuff from how stuff Works dot com

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<v Speaker 1>where smart Happens. Hi Am Marshall Brain with today's question,

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<v Speaker 1>how does the oxygen sensor in a car work? Every

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<v Speaker 1>new car and most cars produced after, have an oxygen sensor.

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<v Speaker 1>The sensor is part of the emissions control system and

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<v Speaker 1>it feeds data to the engine management computer. The goal

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<v Speaker 1>of the sensor is to help the engine run as

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<v Speaker 1>efficiently as possible, and also to produces few emissions as possible.

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<v Speaker 1>A gasoline engine burns gasoline in the presence of oxygen.

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<v Speaker 1>It turns out that there's a particular ratio of air

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<v Speaker 1>and gasoline that's perfect, and that ratio is fourteen point

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<v Speaker 1>seven to one. If there is less air than this

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<v Speaker 1>perfect ratio, then there's gonna be fuel left over after combustion.

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<v Speaker 1>This is called a rich mixture. Rich mixtures are bad

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<v Speaker 1>because the unburned fuel creates pollution. If there's more air

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<v Speaker 1>than this perfect ratio, then there's excess oxygen. This is

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<v Speaker 1>called a lean mixture. A lean mixture tends to produce

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<v Speaker 1>more nitrogen oxide pollutants, and in some cases it can

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<v Speaker 1>cause poor performance or even engine damage. The oxygen sensor

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<v Speaker 1>is positioned in the exhaust pipe and can detect rich

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<v Speaker 1>and lean mixtures. The mechanism in most sensors involves a

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<v Speaker 1>chemical reaction that generates a voltage. The engine's computer looks

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<v Speaker 1>at the voltage to decide if the mixture is rich

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<v Speaker 1>or lean, and it adjusts the amount of fuel entering

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<v Speaker 1>the engine accordingly. The reason why the engine needs the

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<v Speaker 1>oxygen sensor is because the amount of oxygen that the

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<v Speaker 1>engine can pull in from the outside air depends on

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<v Speaker 1>all sorts of things like the altitude, the temperature of

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<v Speaker 1>the air, the temperature of the engine, the barometric pressure,

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<v Speaker 1>the load on the engine, et cetera. When the oxygen

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<v Speaker 1>sensor fails, the computer can no longer sense that air

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<v Speaker 1>fuel ratio, so it ends up guessing and your car

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<v Speaker 1>performs poorly or uses more fuel than it needs to

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