Mass Air Flow (MAF) Sensor – Measuring Air Volume, Density, Temperature

Mass Air Flow (MAF) Sensor - Measuring Volume, Density, Temperature
Mass Air Flow (MAF) Sensor - Measuring Volume, Density, Temperature

So, almost all newer vehicles on the road today, use a mass air flow (MAF) sensor.

The mass air flow (MAF) sensor, measures the volume and density, of the air entering the engine.

Furthermore, the mass air flow (MAF) sensor, also measures the temperature of the incoming air.

The mass air flow (MAF) sensor is always located, in the air stream, before the throttle body. There actually are a few different types, of mass air flow (MAF) sensors.

Hot Wire Mass Air Flow Sensor (MAF)
Hot Wire Mass Air Flow Sensor (MAF)

I would say the most common one used today is what is known as, the “hot-wire” (MAF) sensor.

So, when air passes across the (MAF), it cools the wire inside. As a result, increasing the amount of current needed, to keep that wire, at the specified temperature. Hot wire sensors typically have an operating range of 0 – 5 volts. With idle voltage being around .5 – .8 volts. And, full throttle being between 4 and 5 volts.

So, the voltage required is proportional to the amount of the air flow. The computer uses this information, in conjunction with input from other sensors; to calculate the correct amount of fuel, to deliver to the engine.

Symptoms of a Faulty, Mass Air Flow (MAF) Sensor

So, a contaminated or failed (MAF), cannot measure the amount of air flow correctly. This causes the engine computer to, miscalculate the amount of fuel to be injected. So, a failed mass air flow sensor causes various driveability problems.

Don’t  be fooled, as a faulty mass airflow sensor, can show symptoms similar to low compression or low vacuum. And, can be similar to when your vehicle has low fuel pressure.

Here are some of the most common symptoms, of a faulty mass air flow (MAF) sensor:

  • The engine is very hard to start
  • The engine stalls shortly after starting
  • Your engine consistently runs lean or rich
  • The engine hesitates or drags while under load or idle
  • Hesitation and jerking during acceleration

When your engine runs lean, a failure of the (MAF) sensor can be a likely cause. If your engine is having trouble running or idles erratically; or if the throttle decreases at highway speed it is a possible indicator of a defective (MAF) sensor. A faulty (MAF) sensor, can also illuminate the “Check Engine” light on your dashboard.

Engine Codes For (MAF) Sensor:

Check Engine Light
Check Engine Light

P0100 – Mass Air Flow Circuit Malfunction
P0101 – Mass Air Flow Circuit Range/Performance
P0102 – Mass Air Flow Circuit Low
P0103 – “Mass Air Flow Circuit High”
P0104 – “Mass Air Flow Circuit Intermittent”

Trouble codes P0171 System Too Lean (Bank 1) and P0174 System Too Lean (Bank 2). Can also be caused by a bad or contaminated (MAF).

Before you replace your (MAF) sensor, there might be a chance, a cleaning is all you need.

Cleaning a (MAF) Sensor

Mass Air Flow (MAF) Sensor Cleaner
Mass Air Flow (MAF) Sensor Cleaner

Sometimes you can get away with just cleaning the sensing wire with (MAF) sensor cleaning spray. Avoid touching the wire. And, never clean the wire with a rag or cleaners, not intended for a (MAF) sensor or electrical contacts. Most people like to clean it on the vehicle, but I always remove it first.

It is a easy job and that way it allows for a better inspection. Always inspect the connector for dirt and corrosion, as that could also be the problem.

Stay tuned for another post on, testing and troubleshooting your, Mass Air Flow (MAF) Sensor.


Usually when the sensor is failing, it will let the engine run rich, using more fuel. It will also cause the engine to be sluggish on acceleration. Also, a engine running this way will eventually develop some other problems.

The raw fuel that makes it out of the engine and into exhaust; will eventually cause the oxygen sensor to fail. Given enough time, the fuel and soot will also ruin the catalytic converter.

Basically, the problem will keep getting worse. And, not fixing it right away, will wind up costing you more money in the long run. Catalytic converters, in particular are a fairly expensive part. So, if you see any of the above symptoms, get it check as soon as possible.

Thank You !