When you get upset with your car and start to think it has a mind of its own, you’re not too far off from the truth. The engine control unit (ECU) is responsible for a number of functions within your vehicle. In fact, modern cars couldn’t run without it. It uses information it gathers from sensors located throughout the vehicle to ensure everything stays in optimal running condition and alerts you when it’s not.

What information the sensors pass along

  • The coolant sensor tells the ECU the temperature of the coolant in the engine to let it know if the engine is running warm.

  • The oxygen sensor provides data about how much oxygen is in the exhaust system so the ECU can alter the fuel mixture to reduce emissions.

  • The manifold absolute pressure (MAP) sensor tells the change in frequency or voltage in the manifold pressure. The computer uses this data to alter ignition timing by speeding it up or slowing it down.

  • The throttle position sensor changes the resistance with the opening and closing of the throttle. This information allows the ECU to monitor acceleration and deceleration and idling with the correct fuel mixture.

  • The mass airflow sensor or MAF sensor measures the amount of air going into the engine. The ECU can alter the fuel mixture as more or less air is available.

  • The vane airflow (VAF) sensor performs the same function as the MAF but with a rheostat that is moved by air pushing against a spring-loaded trap, which results in an electronic signal.

  • The manifold air temperature (MAT) sensor monitors air density so the computer can alter the fuel mixture.

  • The crankshaft position sensor provides information about the position of the crankshaft and the cylinder. The data allows the ECU to control ignition timing and the way the fuel injectors operate.

  • The knock sensor monitors vibrations from the engine, allowing the ECU to slow down timing.

  • The barometric pressure sensor checks the barometric pressure, which monitors changes in altitude.

  • The vehicle speed sensor provides information about the speed of the vehicle to regulate shifting and torque converter clutch lockup.

All of these components must be in working order to keep your engine operating smoothly and efficiently. The computer “brain” relies on each one so you don’t have to think about what your vehicle is doing.

This article originally appeared on YourMechanic.com as How Your ECU Uses Sensor Data and was authored by Joyce Morse.

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