Skip the auto shop - Our mechanics make house calls

How Your ECU Uses Sensor Data


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.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.


Post a question and get free advice from our certified mechanics.


More related articles

Insurance Requirements for Car Registration in Kentucky
The Kentucky Transportation Cabinet requires that all drivers in Kentucky carry liability automotive insurance, or “financial responsibility” in order to operate a vehicle legally and maintain vehicle...
The Traveler’s Guide to Driving in Malaysia
CraigBurrows / Malaysia is a popular destination for many tourists today. The country has amazing sights and attractions that you will want to explore....
P2422 OBD-II Trouble Code: Evaporative Emissions Control System (EVAP) Vent Valve Stuck Closed
Diagnostic Trouble Code (DTC): P2422 P2422 code definition Evaporative Emissions Control System (EVAP) Vent Valve Stuck Closed Related Trouble Codes: P2441: EVAP Vent Valve Stuck Open EVAP trouble...

Related questions

Q: Transmission does not give out much power while accelerating.

It sounds like you may have a misfire. What are the codes that you are getting? It could be caused by ignition components or a faulty sensor like the mass air flow or throttle position sensor. Reading the codes should...

Q: Car leaking oil and running rough

If these issues have all started right after the work was performed, then the oil leak needs to be found. It is possible that it is just a loose oil filter. If the engine started running rough right after then...

Q: Air conditioning light - 2001 Honda Civic

Hi there, check the A/C relay for being stuck in the "On" position. Relay contacts degrade over time and use, and can stick together when burned. The result would be the A/C light staying on, even though you press the...