How to Test a Mass Air Flow Sensor? (3 Ways To Do)

The mass air flow sensor is an electronic fuel injection system that measures the density and volume of the air entering the engine. The computer then calculates the best air-fuel ratio based on the measurement and adjusts the vehicle air-fuel ratio and spark timing accordingly.

If the sensor fails to measure the airflow, the vehicle will face several issues. You should test the sensor if you suspect a vehicle malfunction occurs due to the faulty air flow sensor. Then, take further steps.

The article will help you know a few easy ways to test a mass air flow sensor if you think that the MAF sensor is the cause of the malfunction.

How to Test Mass Air Flow Sensors? (3 Ways To Test) 

Testing the MAF sensor is necessary to know whether the sensor has any defects. To test the mass air flow sensor, you must first locate its location. Generally, most of the vehicle’s mass air flow sensors are located between the air filter box and the intake manifold. Also, in some car models, the mass air flow sensor is located inside the air filter intake. 

After locating the sensor, you can test it using a multimeter, scanner or lab scope. All methods are shown in the below sections:

1. How to Test Mass Air Flow Sensor with a Multimeter? 

You can easily test the mass air flow sensor with a multimeter by using the connector harness of the sensor. Generally, the connector comes with a three, four or five pin depending on the vehicle. The good thing is the process is quite the same for all of them. 

Also, if you don’t know the wiring diagram, you first need to find out the actual wire before testing the sensor. Don’t worry; the step-by-step process below will help you know about the diagram and testing process.

Step 1: Find the Wiring Harness

First, switch on your vehicle without turning on the engine. Open the hood of your car and find out the MAF sensor. Then just follow the wiring from the sensor, find the connector, and remove the connector.

Step 2: Know About the Harness Wires

The four wire connector harness has four pins which are:

  • Constant voltage supply
  • Constant ground
  • Sensor signal wire 
  • Sensor ground

Step 3: Finding Ground 

You need to find a good ground to connect the multimeter’s black lead. For this, you can use the battery for better ground.

Step 3: Identify the Constant Voltage Supply Wire

To measure the constant voltage, you must set up the multimeter on gauge 20, DC voltage. Take the red test lead and connect it with the connector pins one by one. If any pins provide a 12 or 5-volt reading on the multimeter, that is the supply wire. 

Now, write down the pin wire color. In our case, the supply wire is red color.

Step 4: Find Constant Ground Wire

To find the constant ground wire, you need to put the multimeter settings to ohms. Now start checking the pin from the right bottom pin. If that is the constant ground wire, you notice a reading on the multimeter. Now, write down the color of the wire.

Step 5: Identity the Sensor Signal Wire

You cannot identify the signal wire without re-attaching the connector. So, connect it first, then back probe the remaining wires. Now, back the multimeter settings to 20 volts. 

Insert the multimeter lead through the remaining wires. However, if you find it difficult to enter the multimeter lead when back probing, use a fine nail or a paperclip into the connector.

Now measure the voltage. The voltage of those wires will be 0 and 0.5 to 0.7 volts, respectively. The wire that provides the 0.5 to 0.7 volts is the desired sensor signal wire. Also, the volt might increase or decrease depending on the vehicle model. That means the remaining one is sensor ground.

Step 6: testing process

Remove the multimeter’s black lead from the battery, connect it to the sensor ground, and put the positive lead on the sensor signal wire.

Then, ask your assistance to turn on the engine and accelerate the engine. The volt meter reading will start increasing if the mass air flow sensor is good. This means your MAF sensor doesn’t face any issues.

If you don’t want to apart the connecter and do the testing process, then follow the below visual guide:

2. How To Test A Mass Air Flow Sensor With a Scanner?

If you don’t want to open the vehicle hood to test the MAF sensor, then the best way is to use an OBD2 scanner tool. Also, it will provide you with more information and an easier way than a multimeter. A scanner tool will give you a waveform and numeric information about the voltage increasing and decreasing to understand easily.

Follow the below steps to test the mass air flow sensor using a scanner tool:

Step 1: First, locate the OBD-II port, which you will find beneath the dashboard. If you don’t see the port there, check the user manual. Then connect the OBD-II tool to the port and turn on the vehicle and scanner.

Step 2: Then, select your vehicle model or use the auto-detect option. To enter the menus, you need to confirm your vehicle profile. 

Step 3: Go to the “Diagnosis” option and then “Control Unit”. Also, don’t forget to turn on the engine. 

Step 4: Afterwards, go to the “Drive” menu and select “Engine-DME Motor Electronics”. Then, you will find the “Live” option and go there and “Motor Operating Values”.

Step 5: Finally, you will find the “Air Mass Flow” option, where the voltage value and unit will be mentioned on the right side.

Step 6: Now, accelerate the vehicle to test whether the mass air flow sensor is working. The value will increase if the Mass Air Flow Sensor works properly after accelerating the car. Otherwise, it will stay the same, indicating the MAF sensor’s malfunction.

Step 7: If you want to inspect the value using waveform, click on the arrow icon near the Air-mass flow option. Then, you will show a graph icon, and the value will now transform into a waveform. 

When you accelerate the vehicle, it will make a wave which indicates the mass air flow sensor is working correctly.

2. How to Test Mass Air Flow Sensor With Labscope?

If you want a more detailed test of the mass air flow sensor, then nothing will be better than the lab scope. It will provide you with waveform data, and you can pause to analyze when needed. Follow the below steps to test the MAF sensor using lab scope:

Step 1: Back probing the lab scope lead with the sensor signal wire and turn on the lab scope. Now, go to Scope Multimeter. Then, you need to go to the test section of mass airflow. 

Step 2: In the test screen, you will get a graph where the voltage scale on the left side is a vertical line, and the horizontal line refers to the time base. When you accelerate the engine, then it will gradually wave, indicating that the MAF sensor works properly.

3. How to Test Mass Air Flow Sensor Without a Multimeter?

If you want to test the MAF sensor without a multimeter and scanner tool, then follow the method. You will find an electrical harness connected to the sensor. When the air flows through the sensor, you must pull out the plug.

If the sensor is good when you pull out the plug, the engine will stop, indicating the MAF sensor hasn’t any defect.

Faqs

When is it necessary to test a mass air flow sensor?

If your vehicle eject black smoke from the tailpipe or the engine runs rough or backfires, it means your vehicle’s MAF sensor is facing issues. If you suspect that a malfunction of the vehicles occurs due to the MAF sensor, it is necessary to test a mass air flow sensor to know whether it works.

What to do after testing the mass air flow sensor?

After testing the airflow sensor, if the signal wire fails to provide the right amount of data, you need to change it. If there is no problem, connect the harness correctly and check whether the air flows appropriately through the sensor.

What is a regular MAF sensor reading when testing?

The sensor voltage reading will differ slightly from vehicle to vehicle. Generally, the sensor signal wire should provide a register of 0.5 to 0.7 volts at idle. The multimeter will provide between 1.5 and 3.0 volts when accelerating the engine. 

How long does it take to test the MAF sensor?

It depends on which procedure you are going to follow. If you test the mass air flow sensor using a scanner tool, you need to spend around 5 minutes on the process. Using a multimeter will take up to 10 minutes, including identifying the wiring time.

Conclusion

If your vehicle experiences poor drivability issues, it might occur due to a bad mass air flow sensor. But it doesn’t mean you should change the sensor without properly inspecting it. You need to find out whether it is working or not by testing it. 

So, in this regard, the guide will help you to know how to test a mass air flow sensor. Also, some methods mention picking anyone you find idle for you.

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