P0100: Mass or Volume Air Flow Sensor A Circuit
A generic powertrain (engine and transmission) trouble code, same meaning on every brand.
Driveable in fallback mode - expect poor economy and flat throttle response.
Symptoms
- Hesitation and surging
- Hard starting
- Noticeably worse fuel economy
Likely causes, most common first
- Mass air flow sensor dirty or failed
- Air leak between the sensor and the throttle body
- Wiring or connector fault
- Filter installed incorrectly or aftermarket intake fitted
Read P0100 yourself before paying for diagnosis
A basic Bluetooth OBD-II scanner ($20-40) plugs into the port under the dashboard and shows this code with live sensor data on your phone - useful both for confirming the fix and for talking to a shop from an informed position.
What is going on and how it gets diagnosed
P0100 is the general circuit code for the mass air flow sensor - the part that tells the computer how much air is entering the engine. Fuel quantity is calculated from that number, so a wrong or missing reading affects everything from cold starts to highway economy.
Start with the intake tract rather than the sensor. Any unmetered air entering after the sensor - a split duct, a loose clamp, a badly seated air filter - produces the same complaint as a failed sensor and costs a fraction to fix. If the ducting is sound, cleaning the sensing element with proper MAF cleaner is the next cheapest step; never touch the wire itself.
Repair options and cost
Typical US independent-shop ranges, parts and labor. Dealers run higher; regional labor rates vary.
Owner reports mentioning P0100
“This has been an issue slowly getting worse over the last few months and escalated this week. June 20th, 2025 my car has literary died over (4) times during traffic and I had to try and stay calm while using a code reader to clear the codes to get the engine to start. Very scary, I have a 2017 Giulia Ti that just hit 100k miles. Even took it to the dealership and they couldn't explain it. Parasitic draw on my battery and they gave it a pass :( Codes: P2510-ECM/PCM POWER RELAY SENSE CKT RANGE/PERFORMANCE P0103-VAF CIRCUIT HIGH INPUT P0100- VAF CIRCUIT MALFUNCTION P0451-EVAP SYSTEM PRESSURE SENSOR/SWITCH 'A' RANGE/PERFORMANCE P0106-MANIFOLD ABSOLUTE PRESSURE/BAROMETRIC PRESSURE SENSOR CIRCUIT”2017 Alfa Romeo Giulia · Jun 2025
“Drive train malfunction came on and veh started to act very different like check engine lights and a lack of power !!! had it sent back to the dealer they switch #4 coil pack to # 5 and the code cleared . Then about 1500 miles later the same thing happen ,so I changed plugs& wires and still the same thing happen again so then I received a P0100 code and P0172 so I changed the pcv and both Mas sensors plus the turbo filters !!!!! still no change ?????”2014 BMW X5 · Sep 2023
“The brakes will activate by themselves with no foot on brake. With no notice it will turn into a full panic stop. Simply driving and all of a sudden the brakes go to full lock. A very very dangerous situation. Once the speed gets below a certain mile per hour it changes. If one stops and turns the engine off and restarts its fine. This started early this year and now has become more frequent. The last 2 times car was driven this has happened. When it is scanned its coming up with 2 u codes p0100-20 and p0121-20”2009 Ford Taurus · Aug 2017 · 113,000 mi
Show 1 more owner reports
“Solenoid that communicates with the transmission and the computer. (this was causing the the stability trac to kick on and sometimes shut the car off while driving or sitting still turning) they also discovered that the entire rear differential had to be replace. This is a 2013 cts coupe 69000 miles when purchased. I contacted gm corporate office for assistance. (p0101 ,p0100, u0101, lost of communication to tcm.”2013 Cadillac CTS · Jul 2016 · 71,000 mi
Cars that report P0100 most often
Based on mentions of this code in NHTSA owner complaints.
Frequently asked questions
Can I drive with P0100?
Driveable in fallback mode - expect poor economy and flat throttle response.
How much does it cost to fix P0100?
Typical US repair costs range from $20 for the simplest fix (maf sensor cleaning) to $450 in the worst case. The right number depends on which cause your car has - see the causes list.
Related codes
The codes closest to P0100. They often appear together, and telling them apart is usually what narrows the diagnosis.
Definition per SAE J2012 standard nomenclature. Symptoms, causes and costs are editorial guidance - always confirm with a diagnosis of your specific vehicle.