Signs of a Failing Mass Airflow (MAF) Sensor

Most vehicles use a mass air flow (MAF) sensor to measure the amount of air entering the engine and help ensure the proper air-fuel mixture to keep it running smoothly.

As you accelerate, more air enters your engine; on the flip side, when you slow down, the amount of air decreases. The MAF sensor tracks how much air is coming in and sends data to the engine’s computer, which determines the correct amount of fuel to burn.

The MAF sensor is typically located in the air intake, between the air filter housing and throttle body.

Signs of a failing MAF sensor

A faulty MAF can cause many problems. These are some of the most common:

• Illuminated check engine light: The engine control module (ECM) monitors MAF sensor operation. If the computer detects a problem with the sensor, it turns on the check engine light.
• Poor engine performance: A faulty MAF sensor affects the amount of fuel sent to the engine, hurting its performance. A bad sensor can cause stalling, misfiring and a lack of power.
• Increased fuel consumption and emissions: Without proper input from the MAF sensor, the ECM may miscalculate the amount of fuel the engine needs, leading to worse fuel mileage and higher emissions.

How to fix the problem

Sometimes a malfunctioning MAF sensor can be cleaned to restore performance. Most auto parts stores sell a dedicated cleaner to be sprayed on the sensor’s heating element. If cleaning doesn’t work, the sensor will need to be replaced.

In most cases, replacing or cleaning the MAF sensor is a straightforward job that most DIYers can tackle. Keep in mind though, a scan tool or code reader will be required to clear any trouble codes and turn off the check engine light. If you don’t feel comfortable taking on this job, a repair shop can take care of it for you.

» MORE: Get an estimate for your MAF sensor replacement

How the MAF sensor works

There are two common types of MAF sensors: hot film and hot wire. Both designs contain a heated element that’s inserted in the air intake stream. Incoming air passes over the element, changing the amount of current needed to keep it hot. The ECM measures how much current is needed to keep things toasty and determines airflow from the calculations.

Not all vehicles have a MAF sensor. Some have what’s called a speed density system, in which the ECM uses data from several other sensors to calculate airflow.

Some vehicles have a separate intake air temperature (IAT) sensor which, as the name implies, is used to measure the temperature of the air entering the engine. Others, however, use the MAF sensor to determine intake air temperature, eliminating the need for a separate sensor.

A typical MAF sensor has three wires — power, signal and ground — going to it. The power wire heats the internal element and the ground wire completes the circuit; the signal wire provides sensor data to the ECM. There will be additional wires if the IAT is integrated into the MAF sensor.