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Mass Air flow Sensor (MAF): how it works, symptoms, problems, testing

Updated: July 09, 2021

Mass Air flow Sensor (MAF).

The Mass Air Menstruation sensor (MAF) is one of the key components of an electronic fuel injection system in your car. Information technology is installed between the air filter and the intake manifold of the engine. Encounter the diagram. The mass air catamenia sensor measures the corporeality of air entering the engine or the air catamenia.
In modern cars, an intake air temperature or IAT sensor is built in the mass air menses sensor. At that place are few types of air menses sensors, all the same, mod cars use a hot-wire type. Let'southward come across how it works.

How a hot-wire air menstruum sensor works

A hot-wire mass air period sensor has a pocket-size electrically heated wire (hot wire). A temperature sensor installed close to the hot wire measures the temperature of the air near the hot wire.

When the engine is idling, a pocket-size amount of air flows around the hot wire, so it takes a very depression electric current to keep the wire hot.

Toyota mass air flow sensor (MAF).

When yous printing the gas, the throttle opens allowing more air to flow over the hot wire. The passing air cools the wire down. The more air flows over the wire, the more electrical electric current is needed to go on it hot. The electrical current is proportional to the corporeality of air flow. A minor electronic chip installed inside the air flow sensor translates the electrical current into a digital signal and sends it to the engine reckoner (PCM). The PCM uses the air menstruation betoken to summate how much fuel to inject. The goal is to proceed the air/fuel ratio at the optimal level.

In addition, the PCM uses air flow readings to determine the shift points of the automated manual. If the air flow sensor doesn't work properly, the automatic transmission might shift differently too.

Mass air flow sensor bug

Mass Air flow Sensor (MAF) Volkswagen mass airflow sensor.

Issues with mass air period sensors are mutual in many cars, including BMW, GM, Volkswagen, Mazda, Toyota, Nissan and other brands. The sensor element could become contaminated or damaged.
For case, in some Mazda Skyactiv engines, a failed mass air menses sensor could cause the engine to crank but not to showtime.
An improperly installed or collapsed air filter can crusade the air menstruum sensor to neglect sooner. Over-soaking a washable air filter can also crusade issues with the air menstruum sensor.

Symptoms of a bad mass air flow sensor

A contaminated or failed mass air flow sensor cannot mensurate the amount of air flow correctly. This causes the engine figurer to miscalculate the corporeality of injected fuel.

Mass Air flow Sensor (MAF).

As a result, a bad mass air menses sensor causes various driveability problems, including a no-start, stalling, lack of power and poor acceleration. In addition, a faulty mass air flow sensor might crusade the Check Engine or Service Engine Soon low-cal to come on. A problem with the air flow sensor could also alter the shifting pattern of the automatic transmission.

When the air menstruum sensor bespeak varies from the expected range, the PCM records a fault and stores the corresponding trouble lawmaking, illuminating the Cheque Engine lite on the dash. This problem code tin exist retrieved with a browse tool. The following trouble codes are usually associated with a mass air flow sensor:
P0100 - Mass Air Menses Circuit Malfunction
P0101 - Mass Air Flow Excursion Range/Performance
P0102 - Mass Air Menses Circuit Low
P0103 - "Mass Air Flow Circuit High"
P0104 - "Mass Air Menstruation Excursion Intermittent"
Trouble codes P0171 System As well Lean (Bank i) and P0174 System Too Lean (Banking concern 2) are as well frequently caused by a bad or contaminated mass air flow sensor.

How the mass air menstruation sensor is tested

In modern cars, the only way to examination the mass air flow sensor is with a scan tool. Mechanics measure the amount of air flow (mass air catamenia sensor readings) at different RPMs. They compare the readings to the specifications or to the readings of a known-practiced mass airflow sensor.

Testing Mass Air flow Sensor (MAF) Mass Airflow Sensor (MAF) readings of a two.4L iv-cylinder engine at different RPMs.

Often mass air menstruation sensor readings are measured at idle, i,000 RPM, ii,000 RPM and three,000 RPM. A contaminated or bad air menses sensor will, in most cases, show lower air flow readings than a known good one. In some rare cases a bad sensor may testify college readings. Of course, different engines will take unlike readings. The air catamenia depends on the engine volume, and then a V6 or V8 engine will have higher readings.

Low mass air flow readings do not hateful the sensor is bad. A clogged up air filter or plugged catalytic converter can also cause lower air catamenia sensor readings. Vacuum leaks affect air period sensor readings too. That's why mechanics use a known-good sensor to compare the readings. Read more: Vacuum leaks: common sources, symptoms, repairs.

Is there a way to bank check the mass air flow sensor readings at domicile? Of form, for instance, here nosotros used the gratuitous Torque app to measure the mass air catamenia sensor readings at different RPMs (in the photo). This mass air flow sensor is good.

To use any phone app that connects to your auto, you lot will need a Bluetooth adaptor that plugs into the OBD connector.

Sometimes a poor electric connexion at the air flow sensor connector could besides cause the air flow readings to be out of range. For this reason, the air flow sensor connector terminals too as the wiring needs to be carefully inspected.

Often if an air filter is not installed properly, or the air filter box is not airtight, a slice of droppings tin go sucked into the mass air flow sensor (meet this photo) and crusade issues. Sometimes the debris can fall in during the air filter replacement. In this case, the repair is easy. The mass air flow sensor must be cleaned and the air filter must be reinstalled correctly or replaced.

Air menses sensor replacement

If the air menstruum sensor is bad, information technology needs to be replaced. It'southward a fairly uncomplicated job. The part costs from $89 to $380. If a sensor is dirty, your mechanic may suggest cleaning it (cleaning the airflow sensor is a fragile procedure) every bit a temporary solution; sometimes information technology could aid. When replacing the mass air catamenia sensor, make sure the air filter is installed properly.