How to Reset the Mass Air Flow Sensor – Plus Obvious Signs of a Maf Problem!

The function of a mass air flow sensor in a car is to determine the mass flow rate of air into an engine. Doing so allows for the correct balance of air and fuel to be present for combustion.

As you can imagine, the sensor is critical to the optimal functioning of your engine.

Having a problem with the mass air flow sensor is not something you can ignore for too long.

Several problems may affect your car’s performance and result in higher repair costs. Knowing how to identify a problem with the sensor and reset the mass air flow sensor in your car is vital.

Signs of a Problem With Mass Air Flow Sensor

There are several telltale signs that your mass air flow sensor is malfunctioning. Let’s go through them before you set out to reset your mass air flow sensor.

Black exhaust fumes

Black exhaust fume is the most noticeable indication of a mass air flow sensor problem. The inside of the tailpipe will also be thick with black soot. This happens when there is too much fuel in the combustion chamber. It’s a dead giveaway that the sensor isn’t working correctly.

Checking to see if there is any carbon buildup in your car’s exhaust, could also indicate an issue with your catalytic converter or other parts. These problems can cause increased pressure, and toxic fumes released into your vehicle’s cabin.

Trouble starting

There may be an issue with your mass air flow sensor if you are having trouble starting your vehicle or if it idles rough.

Your car requires adequate air and fuel to start, and not having either, or the correct amount may delay or reduce the chances of the car starting.

Fuel usage

If the mass air flow sensor fails, you may notice an increase in fuel consumption.

In this case, too much fuel enters the combustion chamber. As a result, your gasoline will be depleted faster than usual.

Problem with acceleration

This is a common side effect of mass air flow sensor malfunctions. You will not be able to accelerate or rev smoothly without the appropriate mix of air and fuel.

When you try to accelerate farther, you may notice a slight shudder in the car.

Check engine light

Let’s say that the check engine light comes on along with any of the above signs of a defective mass air flow sensor.

In that case, you could presume it is the mass air flow sensor, but without plugging the car into a diagnostic machine, it would be unwise to presume. A lot of other sensors share similar faults.

Resetting Mass Air Flow Sensor

Resetting the M.A.F. sensor first requires one of two things to happen first.

  1. Replace an old defective sensor if you are sure it needs replacing.
  2. Remove, the sensor give it a clean, refit and reset the sensor (most people would try this first as it can usually cure a fault).

You will first need to locate the sensor and remove it. The MAF sensor can usually be found on the intake pipe, the airbox, and the inlet manifold. They come in all different shapes and sizes. Some are just tiny sensors that plug into the pipe; others are a 6-inch section of pipe with a honeycomb pattern internally.

Unfortunately, regardless of how you reset the M.A.F sensor, you may need to use a diagnostic machine to clear the fault code. Sometimes you can remove fault codes by disconnecting the battery (which works on older vehicles), but modern cars are a little more complex now—leaving you with only a reset using an OBD2 code reader.

Idling the engine

To reset the sensor by idling the engine, wait until the engine is cool before you start. 

  1. Remove the mass air flow sensor by pulling its plug and disconnecting the wire harness.
  2. This is where you either clean your sensor or decide whether to replace it.
  3. Start your car without the mass air flow sensor and leave it idling for a few seconds (less than 10).
  4. Switch off the vehicle and reattach the mass air flow sensor to its harness.
  5. An error message or engine management light may pop up on your dashboard. You’ll have to clear the memory to get rid of the error.
  6. Restart your car, and voila!

Disconnecting the battery

The second way to reset the mass air flow sensor is to disconnect the battery.

  1. First, remove the mass air flow sensor.
  2. Disconnect the car battery and leave it this way for 10 minutes
  3. Then, place the cleaned or new mass air flow sensor back into its harness.
  4. Start the car, and your system should be reset.


  1. When should you reset a mass air flow sensor?

You should reset your mass air flow sensor after cleaning or replacing it. If you don’t reset it, your car could run rough and the mpg will be reduced.

  1. Does the mass air flow sensor have to be calibrated?

Yes. Your mass air flow sensor must be calibrated for your car’s injector size. The sensor cannot function properly if it is not correctly calibrated. Usually, they will be calibrated for your car’s specific make, model, and engine size. If you are unsure which sensor to get, take the old one with you when you buy one to check it is correct before fitting an incorrect part.

  1. Is it better to clean or replace a mass air flow sensor?

Your mass air flow sensor should be cleaned each time your car is serviced. However, this isn’t the case. Keeping it clean will prevent any complications with your car. The only time you should replace your mass air flow sensor is if there is damage to the sensor. Otherwise, proper cleaning will suffice to get your car running optimally.

In Summary

To put it simply, the mass air flow sensor is crucial for your car to run correctly. If the mass air flow sensor fails, you will likely face many performance concerns. Luckily, it’s pretty easy to clean and reset your mass air flow sensor.

You only need to replace the sensor if there has been any damage. It is possible to reset your sensor using two methods, both of which you can do yourself if you are familiar with car engines and batteries.

However, if you are unsure what to do, it is best to visit your mechanic to reset your sensor.

My name is Tom although my friends call me Tommy. Messing around with cars and bikes has always been a hobby of mine even from a young age. So I made it my day job 17 years ago. I am a fully qualified mechanic as you would expect. I've worked in all different areas of the motor trade, valeting, panel beating, engine repairs, I'm sure you get the idea. I enjoy sharing my wealth of knowledge and experience with others, which is the reason I spend a lot of time here writing for this website.

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