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P0101 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


Mass or Volume Air Flow Circuit Range/Performance Problem


Typically, we see the OBD-II code P0101 when the signal from the mass air flow (MAF) sensor is out of expected range (too high or too low).  

In layman’s terms, it means the MAF sensor is malfunctioning or failing to function period. The good news is that in most cases, the cause of this trouble code is often easy to diagnose.


There are many reasons your vehicle may give a code P0101, and we’ll list them here for you.

  • MAF sensor is obstructed, dirty or faulty
  • The snorkel/boot on the MAF intake is torn, cracked or disconnected/loose.
  • MAF sensor cannot maintain a vacuum seal (PCV valve stuck open, vacuum leaks/faulty intake gaskets, etc.)
  • Air filter is clogged or installed improperly
  • MAF sensor element malfunction caused by excess oil from an oil-soaked air filter
  • Catalytic converter is partially or completely blocked, or the exhaust airflow is restricted

Other possible causes for a code P0101 are:

  • Throttle body is dirty and requires cleaning
  • Faulty or contaminated manifold absolute pressure sensor (MAP)
  • Worn or damaged electrical connections, worn or faulty connectors on the MAF sensor
  • Jammed EGR valve
  • Valve timing is not correctly configured
  • Engine computer (PCM) is faulty or disconnected


Your vehicle is going to experience the following if you have a problem with your mass air flow sensor:

  • Stalling (typically while idling)
  • Difficulty starting/turning over
  • The engine starts and stalls out 
  • Low power when accelerating
  • Unstable idle that results in stalling


Our technicians have a well-established process for determining what is causing a code P0101. Here’s our step-by-step procedure:

First, our technician checks the mass air flow sensor to see if it just needs a quick cleaning. Occasionally they find a foreign object like a leaf or dust buildup is interfering with the measuring element (hot wire), triggering the trouble code.

Next, our technician will check the air filter and try to get information about whether it has been recently changed. If the problem started around the same time as an air filter exchange, we check to see if the air filter was properly installed and the MAF will be inspected for obstruction as well.

Certain makes of car (e.g. Volkswagen) implement have a fine metal mesh over the air filter intake installed to help prevent the air filter or MAF from being clogged by large debris (leaves, dirt etc.). If your car uses this type of filter mesh, our technician will also check and clean this mesh filter, too.

After checking the air filter, our technician will visually inspect the intake boot for physical damage (cracks, tears, loose clamps, etc.). Vacuum leaks or damages in the intake boot are common in many European-made vehicles like BMW and Volvo.

Once the boot has been checked, the technician will verify no other vacuum air flow seals are compromised as well.

Finally, our technician tests the MAF scan tool using the live data function. The technician captures the  airflow sensor readings at different RPMs (e.g. 1000, 2000, 3000) and compares their readings to known MAF readings from a fully functional MAF sensor.

Faulty airflow sensors are a common occurrence in many cars, and it is usually requires a fairly simple repair to correct the P0101 code.

Common mistakes

It’s fairly common for DIYers and some technicians to just exchange the MAF sensor with a new one without completing the entire diagnosis process for MAF problems.

Not only is this more costly for the owner of the vehicle, but it may not fix the P0101 problem if you have a cracked intake boot, dirty air filter, or your air filter intake mesh needs to be cleaned.

How serious

The good news with the OBD-II code P0101 is it does not pose any danger to the driver and won’t prevent your vehicle from running.

Conversely, a faulty mass air flow sensor increases fuel consumption and make your engine run rough.

Continuing to drive a car with P0101 airflow issues may lead to much more serious and expensive engine damage, so you should definitely take it in to a licensed automotive service center to have the root cause of the problem resolved.

What repairs can fix the code

repair manuals

The simplest solution is to reset the computer and see if the P0101 code comes back. Sometimes a temporary obstruction causes your vehicle to display a P0101 code.

If a reset doesn’t fix the issue, a smart technician will test the engine performance for symptoms and see if the problem recurs. If your car continues to exhibit MAF flow problems, the technician will continue through the diagnostic process.

Additional diagnostic and repair information varies by the particular make and model of your vehicle.

If it’s determined that the P0101 code is the result of an improperly installed air filter, simply remove and reinstall it correctly.

Also, it’s a good idea to check the air filter for significant debris or damage to the filter medium. If it’s filthy and worn out, it needs replacing.

The wiring harness for your MAF sensor cannot be too close to the MAF, air filter or other air flow components.

If your inspection turns up an improperly routed wiring harness, then it will need to be rerouted before the P0101 issue can be resolved.

Can a dirty air filter cause a P0101 code?

A contaminated MAF sensor element can cause the code P0101 or other MAF-related codes in vehicles with aftermarket air filters soaked in oil. Occasionally, Volvo cars exhibit the fault code P0101 if their throttle bodies are dirty or their PCV system is leaking vacuum.

Also read: 6 Easy Steps On How To Clean A Car Air Filter

Related codes


If you see a P0101 code come up on your OBDII scanner, you have an airflow issue.

A qualified technician should make a complete inspection of your air flow system components and test the sensor to ensure it’s reading airflow correctly.

Once the root cause of the error is established from a skilled diagnosis, fixing code P0101 generally takes little time and is not prohibitively expensive.

P0101 Code – What Does It Mean & How To Fix It