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

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

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

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

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

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

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; 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. As a result; 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 Sensor (MAF)

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. As a result; 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 sensor (MAF);

  • 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) are also often 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 Sensor (MAF) Cleaner
Mass Air Flow Sensor (MAF) 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 allows for better inspection. Always inspect the connector for dirt and corrosion as that could also be the problem as well.

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

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