OBD2 Codes

P0101 – Meaning, Causes, Symptoms, & Fixes


What Does Code P0101 Mean?

  • P0101 definition: Mass Air Flow (MAF) Circuit/Performance Malfunction
  • Issue Severity: MODERATE – Extended driving with this code can cause internal engine damage.
  • Repair Urgency: Get this code fixed as soon as possible to avoid internal engine failure.
  • Diagnosis: Code P0101 does not pose any danger to the driver and will not prevent the vehicle from running. However, it will cause an increase in fuel consumption and rough operation. Sustained driving can lead to internal engine failure.

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The mass air flow (MAF) sensor measures the amount of air entering the engine. Check engine light code P0101 is set when the measurement of air entering the engine by the mass air flow sensor is outside of the manufacturer’s specified range.

P0101 Causes

There are many potential causes of code P0101. Some are easy to check and correct yourself, such as a dirty air filter or mass air flow sensor. Other causes are more complicated, such as a vacuum leak or a clogged catalytic converter.

  • Dirty, obstructed, or faulty mass air flow sensor
  • Damaged or disconnected air intake boot (snorkel)
  • Vacuum leak
  • Clogged or improperly installed air filter
  • Clogged catalytic converter / restricted exhaust

P0101 Symptoms

  • Engine stalling
  • Difficulty starting
  • Lack of power
  • Rough idle

How Do I Fix Code P0101?

With a mass air flow sensor fault, the first step is to get it diagnosed to figure out what is causing the problem. 

If your vehicle has this fault and you’re not comfortable diagnosing this issue at home, we recommend finding a RepairPal certified shop nearby to pinpoint the problem and give an accurate estimate for repairs. 

These shops can not only help you figure out what’s going wrong before you waste time and money on the wrong parts, but they also offer a minimum 12-month, 12,000-mile warranty and stand behind all their estimates with guaranteed fair pricing.

> Find a RepairPal Certified Shop Near You

How Much Does It Cost to Fix Code P0101?

P0101 can be caused by anything from a dirty air filter to a clogged catalytic converter. It’s impossible to give an accurate estimate without properly diagnosing the issue first. 

If you take your car to a shop for diagnosis, most shops will start with an hour of “diag time” (the time spent in labor diagnosing your specific issue). Depending on the shop’s labor rate, this typically costs somewhere between $75-$150. Many, if not most, shops will apply this diagnosis fee to any required repairs if you have them perform the repairs for you. From there, a shop will be able to give you an accurate estimate for repairs to fix your P0101 code.

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  • Upfront cost estimates
  • Minimum 12-month, 12,000-mile warranty
  • Fair price guarantee

Possible Repair Costs for P0101

Once properly diagnosed, P0101 may require one or more of the following repairs to resolve the underlying issue. These prices are based on national averages and include parts and labor. Your cost may differ depending on your location and type of vehicle.

  • Air filter $50-70
  • Mass air flow sensor $220-320
  • Catalytic converter $1720-1780

DIY Steps to Diagnose Code P0101

Engine code P0101 could be caused by a number of things, including a dirty air filter, mass air flow sensor, catalytic converter, and more. If you’d like to try to fix code P0101 at home without throwing money at parts, you’ll want to follow the steps below for proper diagnosis. Keep in mind this is an intermediate-level diagnosis and repair and not recommended for beginners. Diagnosis beyond oil level and condition requires more specialized equipment beyond what the FIXD Sensor can provide and it can be a time and labor-intensive process for inexperienced DIYers.

DIY difficulty level: Intermediate

This repair requires mechanical knowledge and is not recommended for beginners.

Tools/parts needed (our top picks from Amazon):


Locate your air intake box that houses your air filter. Open the air intake box using the required tools for your vehicle. Ensure the air filter is seated properly and is clean. Reseat the air filter if it is not seated properly, and replace the air filter if it is dirty. This may be as much as you need to fix P0101, however, we recommend completing step 2 as well. It is not difficult or expensive and may improve performance. 


Remove the wiring harness from the mass air flow sensor and remove the air intake snorkel from the air intake box. Use mass air flow sensor cleaner (DO NOT SUBSTITUTE ANY OTHER KIND OF CLEANER) to clean out the MAF sensor. Do this by spraying each side of the MAF sensor for 3-5 seconds, waiting 10 seconds, and then spraying it again for 3-5 seconds. Do not wipe it. The MAF sensor hot wires are very sensitive, and MAF sensor cleaner cleans and dries very quickly. Reconnect the air intake snorkel, close the air intake box, and reconnect the MAF sensor harness. Clear the check engine light code using the FIXD app and complete several drive cycles to ensure this was the correct fix. Here is a great video to show you this process!


If your check engine light comes back on with diagnostic trouble code P0101, examine the air intake system for vacuum leaks.


If no vacuum leaks are found, the problem is likely a restriction in your exhaust. This could be a clogged catalytic converter, or physical damage to the exhaust itself, causing a restriction that prevents exhaust gases from flowing out of the engine smoothly.

Common P0101 diagnosis mistakes

Buying and installing a new mass air flow sensor without completing the entire diagnosis process.

Still Need Help Fixing Code P0101?

If you’ve followed the steps above and are still experiencing check engine code P0101, please contact the FIXD Mechanic Hotline if you’re a FIXD Premium subscriber or find a RepairPal certified shop near you to get the right repairs at a fair price.


Recovering autocross and track day enthusiast. Once turned a VW Jetta into a pickup truck. Lives in a van down by the river. Dream car: 2001 Subaru WRC rally car.

Justin Hughes
Recovering autocross and track day enthusiast. Once turned a VW Jetta into a pickup truck. Lives in a van down by the river. Dream car: 2001 Subaru WRC rally car.

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    1. Very helpful, never expected to have a way to remedy the problem given also. Very informative.

      1. Thanks,, this let’s me know what to expect when I take it to get repaired

        1. How can it be exhaust stopped up if MAF was making a gear noise

        2. First thing to do is check for recall regarding ECU reprogram.
          Check the condition of MAF.
          Clean or replace (if is necessary) the MAF
          Reset the code and make a test drive.
          If the code persists (sometimes check engine light is not on but the code is the) probably is time to reprogram the ECU.

          1. Roberto,
            Hi i am having the same issue with my vw passat b7. I’m keep getting fault code p0101 after changing air MAF sensor, checked air intake snortel plus wiring and even changed with new air filter. Before changing all these parts I was getting engine on as well but now it is only coil light comes up after 5 miles do I need to reprogram my car’s ECU.

      2. Thanks for information about the mfs. I will get my mechanic on it I will let you know what happens.

    2. So far we love our FIXD. We have already completed the job and now just waiting to see if check light comes back on again. I have a 1997 Miata that we know is running rich and it feels like it is miss-firing but no check engine light. Can FIXD help me diagnose issues without check engine light on? Can you help me with a reliable and honest mechanic in south Georgia/North Florida area that knows how to work on NA Miata? Thanks

      1. Hey Connor! Currently, FIXD only diagnosis when the Check Engine Light is on. In terms of finding a good mechanic, if you go to the tool bar on the right side of the app, there should be an option to “Select Service”. This will help you find a quality mechanic!

        Thanks, FIXD Team

        1. The 2011 Nissan Altima service engine soon light came on. The code says p0101 can anyone tell me what’s that mean. If not fixed what will happened.

        2. FIXD, I installed a cold air intake on my 2009 GMC Sierra 1500 SLE and had the P0101 code come up for the mass air flow sensor malfunction. I remedied all of the problems and my check engine light went away. But my fixd app sensor stills shows the code when I scan it. The code doesn’t go away but there is no check engine light. What should I do as I have had several mechanics take a look at it and I’m a mechanic myself and nobody can figure out why the code is still there. Does it just need to be driven around for a couple hundred miles? I have already driven about 250 miles since the light went away. Please help me.

    3. Didn’t pick it up on the fixd app directly, got this email. Did what I was instructed to do and the problem was however remedied which was nice.

      1. Thank you that was very helpful and inexpensive

    4. Very helpful, thanks for diagnosis steps because the MAF isn’t cheap but it made my car work again
      Thank you once again

      1. No problem Kevin! Glad we could help.

        FIXD Team

      2. What does MAF mean?

        1. Mass air flow

    5. Any help would be appreciated.
      Replaced my MAF censor, intake gaskets, catalytic converters, all 4 o2 censors, map censor, and wire harness for the maf. Engine light still on for maf. Has p0101 p0172 and p0175 codes. Not sure what to do next.

      1. Same here

      2. Sorry mine is a 2012 Nissan Maxima

    6. My 2004 S10 Blazer 4×4 with 95,000 miles has recently been difficult to start intermittently. After several weeks of the occasional hard/long start issues, the SES light came on and my FIXD showed this P0101 code.
      I cleaned my air filter and the MAF sensor and experienced no improvement. So, I then replaced the filter and MAS sensor. Unfortunately, I’m still having the same problems as before.
      Sometimes the vehicle starts right up and sometimes I must keep cranking it (or stop and begin cranking over again) to get it going.
      Any idea what I should do next or what might be causing my problem??
      Thanks. I love my FIXD!

    7. FIXD troubleshooter led me right to an improperly closed air filter box! Replaced the filter and cleaned out the box. Problem solved. Thanks

      1. Not an answer but a question, what code were you getting to be lead to this fix?

    8. as I had already replaced the MAF sensor before receiving FIXD – I connected it & it gave me the same diagnosis that I had already received from 2 other mechanics. I was able to turn off the check engine light – however the car is still rough idling and mpg still fluctuating between 11 – 34 ? any help on this? 2016 Nissan Sentra SV (I also replaced the air filter)

      1. Hi Heather, I wish I had an answer but I’m in the same boat as you with my 2012 Nissan Maxima. I did read in FIXD that if replacing filter and MAF sensor doesn’t resolve the issue it is either a vacuum leak or exhaust issue. If you have found a remedy please let me know.

        1. A vacuum leak will usually cause a lean code,and live air alpha percentages will be in the 120% higher ranges.Vacuum gauge is a very useful tool. If the engine combustion is balanced and no intake,exhaust,PCV. issues.A replacement throttle chamber a correct calibration setup should remedy.Also install any ECU. updates and clear all control DTC’s and clear ECU’s self-learned data.

    9. So I Asked the guy at autozone if he knew what it was NOPE!!!! Now I’m in here leaving this comment with a BIG THANK YOU!!!!

    10. That’s the code FIXD gave me. And, I don’t think this is what’s killing my battery. Seemed like a very good diagnosis, but what does that have to do with my battery, something is killing my battery. Turn off the car, and I might get under 10 minutes before I would need a jump

    11. Why is it important to use the MAF cleaner from Gunk and not another brand such as CRC?

    12. That sounds like a battery or alternator issue. I’d get a multimeter and check if the battery is at good voltage, it might be a dead cell.

    13. I used the Fixd reader to diagnose the problem with my check engine light. I then went to Autozone and purchased a can of Mass airflow cleaner for ten bucks and sprayed the sensor, waited a few moments and put it back together. I then used the Fixd reader to reset the check engine light, problem solved! In my opinion the Fixd reader just paid for itself, on the first use. I would highly recommend this product, no question about it a very worthwhile investment .It’s not very often a product will pay for itself in one use. Thank you.

      1. That’s awesome Pete! Thanks so much for the kind words and thrilled to hear how FIXD helped you with your car problem!

    14. I’ve done everything to try to fix my air flow sensor, or rather…the Check engine” light. even took it to the dealership i bought the car from,and they couldn’t find a problem with it, but at 45,000 miles, it needed a refurbished transmission, which cost $4,800 dollars. So we had to pay $2,400 for our part because we called a consumer protection agency, and our agent was able to make the dealer pay for the other half. It’s a 2012 Maxima and we bought it brand new from that dealership. They would not honor a free transmission because our 7 year warranty was past due by 3 months. They said they tried EVERYTHING, but didn’t know why that light wouldn’t go off. It does affect the mileage and it stutters when it’s bad, otherwise it drives fine.
      I took replaced my air filter and cleaned the sensor, and it stills shows up. It won’t pass emissions.
      I even took it to a different auto shop and had them replace the sensor with a new one from Nissan, and still didn’t charge anything.
      Now it has 48,607 mi. It used to get great mileage, but now it gets about half of what it used to. This car was used primarily by my wife to drive to and from work, which is 7 miles each way. We kept it maintained especially since they were giving all kinds of freebies in order to sell cars.
      We couldn’t understand why they couldn’t label this thing a lemon. After all, what kind of car falls apart at 45,000 Miles?
      We have spent thousands, even using some savings to pay it off 2 years early. Then it breaks down and we had to spend thousands more to find someone to fix it. I can’t believe that with all the machines and special tools, there’s not one real mechanic out there who actually knows their sh*t.

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