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P0104 – Meaning, Causes, Symptoms, & Fixes


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What Does Code P0104 Mean?

  • P0104 definition: Mass Air Flow (MAF) Electrical Circuit Erratic and Irregular Output
  • Issue Severity: MODERATE – Extended driving with this code may cause internal engine damage.
  • Repair Urgency: Get this code fixed as soon as possible to avoid drivability issues and a no-start condition.
  • Diagnosis: The trouble code P0104 can cause the vehicle to have driveability issues and should be taken care of as soon as possible as the continuation of driving could cause other issues within the vehicle.

The Mass Air Flow (MAF) sensor measures the amount of air entering the engine. When code P0104 is set, there is an inconsistent or irregular voltage output to the ECM, PCM, or ECU depending on your car type (check your owner’s manual for your specific car). Due to the inconsistent and irregular nature of this code, diagnosis can be difficult.

P0104 Causes

There are many potential causes of code P0104.

  • Dirty or damaged air filter (common cause)
  • Leaking vacuum hoses or intake gaskets
  • Debris covering MAF sensing element (common cause)
  • Faulty MAF
  • Faulty electrical connection to MAF sensor
  • Corroded/Damaged MAF circuit terminals

P0104 Symptoms

  • Check Engine Light
  • Lower fuel economy
  • Black smoke from the tailpipe
  • Rough operation
  • Stalling
  • Hard Start

How Do I Fix Code P0104?

With a MAF 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 P0104?

P0104 can be caused by anything from a dirty air filter to faulty wiring to a bad MAF sensor. 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 P0104 code.

Possible Repair Costs for P0104

For error code P0104, one or more of the below repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to make the repair.

  • Mass Air Flow (MAF) $300-$400
  • Vacuum leak $100-$200
  • Wiring repair $100-$200
  • Air Filter $20
  • MAF Cleaning $100-$200 

DIY Steps to Diagnose Code P0104

Engine code P0104 could be caused by a number of things, including a faulty or dirty MAF sensor, a vacuum leak, or a faulty MAF sensor. If you’d like to try to fix code P0104 at home without throwing money at parts, you’ll want to follow the steps below for proper diagnosis. Keep in mind that this is an intermediate-level diagnosis and repair and is not recommended for beginners. Diagnosis 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):

  • FIXD
  • Spray bottle of water
  • Basic hand tools


Check your air filter and replace if needed.


Visually inspect wiring around Mass Air Flow (MAF) Sensor for any frayed, broken, corroded wires.


Conduct a visual and audible inspection of the vacuum lines, and any intake connections to make sure there are no signs of disconnection or outside air leaks. This includes the intake pipe between the throttle body and MAF. 

Spray water over the intake area and listen to the engine. If it stumbles and briefly starts running rough, there is an intake leak. Concentrate the stream on different hoses and gaskets until you find your leak.


Clean your MAF sensor to make sure that there are no pieces in the system that do not belong. Check out this article for a step by step walk through of the process.


The quickest way to check if your Mass Air Flow (MAF) sensor is the problem is to disconnect your electrical harness while your car is running. Check your owner’s manual to locate the MAF sensor for your specific car.

NOTE: Make sure that all other parts of your vehicle have cooled down (6-8 hours inactive) before doing this test. Reference this video for visual reference. Doing this test will cause other MAF codes to populate. After this test, clear these codes.

If your car’s engine shuts off, your MAF sensor is operating normally. If it does not shut off it means that your MAF sensor is not operating normally and should be replaced.

Common P0104 Diagnosis Mistakes

Replacing the MAF sensor before checking for a dirty air filter or debris on the MAF sensing element.

Still Need Help Fixing Code P0104?

If you’ve followed the steps above and are still experiencing check engine code P0104, 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.

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Fixed It But The Check Engine Light Is Still On?

Check engine light sometimes need to be reset manually, check out our article:

How to Reset Your Check Engine Light | 4 Ways To Clear It (With or Without a Scanner)

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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About the Author

Justin Hughes

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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