A hand holds an old vehicle oxygen sensor.

5 Car Sensors and Their Functions

Car sensors and their functions may seem complicated, but they’re a simple way to make sure essential systems in your vehicle are operating smoothly. These sensors monitor everything from oxygen levels to air flow to the temperature of the engine coolant. Here are five car sensors and their functions to help you better understand how your engine works.

Oxygen (O2) Sensor

Your engine needs oxygen, but too much or too little can cause problems. These sensors measure the oxygen level in your car’s exhaust and compare it to the amount of oxygen in the air around your car.
Car engine

This determines the ratio of fuel to air in your engine, which is called the fuel ratio. It’s used by the engine’s computer to see if fuel is being metered properly. If this important ratio is off with too much or too little fuel, then your car may not work as efficiently. This can cause performance issues and create excess pollution.

Mass Air Flow (MAF) Sensor

This sensor works along with the oxygen sensor to make sure your engine has the right fuel ratio. While the oxygen sensor is in the exhaust system, the mass air flow sensor is located near the air filter and monitors how much air is flowing into the engine. If your MAF sensor fails, you may notice rough idling or stalling, and your check engine light might illuminate.

Manifold Absolute Pressure (MAP) Sensor

The manifold absolute pressure sensor also measures the air coming into your engine, but in a different way. While the MAF sensor measures the flow of air, the MAP sensor measures the density of the air. This information is used by your engine’s computer to adjust the amount of fuel used in the combustion process and keep the optimum fuel-to-air ratio.

Engine Speed Sensor

The engine speed sensor measures the speed of the crankshaft in rotations per minute, or RPMs. This isn’t the same as clocking how fast the car is going — that is measured by the vehicle speed sensor. The engine speed sensor shows the engine’s speed only, and it is used to monitor the car’s overall performance. If it’s not working properly, you may have issues with your speedometer or the cruise control feature.

Coolant Temperature (CTS) Sensor

As the name implies, this sensor keeps tabs on the temperature of your engine’s coolant. It uses this information to regulate other systems that help keep your engine properly cooled, like the cooling fan. If this sensor malfunctions, your engine can overheat, which is a significant issue. In this case, the check engine light will illuminate to warn you that you should have your engine serviced and refrain from driving.

These are just a few car sensors and their functions to help you better understand the crucial components that keep your car running smoothly. The full list of sensors is long, and they all work together in the background to ensure that your engine runs safely and efficiently so you can go about your day.

Check out all the relays, sensors and switches available on NAPA online or trust one of our 16,000 NAPA AutoCare locations for routine maintenance and repairs. For more information about car sensors and their functions, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photos courtesy of Flickr.

about author

Nicole Wakelin

Nicole Wakelin covers the automotive industry as a freelance journalist for a variety of outlets. Her work includes news pieces, podcasts, radio, written reviews, and video reviews. She can be found in The Boston Globe, CarGurus, BestRide, US News and World Report, and AAA along with lifestyle blogs like Be Car Chic, The Other PTA, and She Buys Cars. She is active on social media with a large following on both Twitter and Instagram and currently serves as Vice President of the New England Motor Press Association.

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