How to Test Mass Air Flow Sensor

How to Test Mass Air Flow Sensor?- A Complete Guide

Few think of airflow range sensors during car maintenance, but their importance far exceeds what you think! 

It’s hard to imagine how your car can control its air combustion and overall performance without these devices. So once spotting any unusual signals, you need to bring them to an auto repair shop immediately!

This article from Bryan’s Garage gladly delves further into how to test mass air flow sensor. Let’s get started!

A Brief Overview of Mass Air Flow Sensors

A Brief Overview of Mass Air Flow Sensors

(Source: Wiki). 

It’s hard to discuss testing tips for mass airflow sensors WITHOUT understanding what they are or how they work. So here’s a quick summary!

What Is It?

A mass airflow sensor (MAF from now on) serves as the biggest key component for a car’s electro-fuel injection program, often placed between the intake manifold in the check engine light and your car’s air intake filter

Certain car models even have an IAT (intake air temp) sensor built directly into the MAF. 

Keep in mind that there is no fixed type of sensor, meaning they require varied maintenance methods. Their output generation also slightly differs. 

For instance, digital sensors transmit frequency outputs, while an analog MAF produces outputs for variable voltages. Both are then stored in the ECM (engine/electronic control modules) for better fuel-air regulation within the automobile transmission system. 

What Exactly Do MAFs Do?

MAFs help you measure how much air mass the engine load takes in, which is crucial for estimating the fuel amount needed to achieve proper fuel-air ratios (FAR). The ideal FAR is 14.8:1 (14.8 air pounds to 1 gasoline pounds), but that can also change across different situations. By way of illustration, acceleration requires a ratio of 12:1; meanwhile, cruising cuts that number down to 22:1. 

Keeping the MAF at optimum performance peak is important. Otherwise, faulty or malfunctioning ones make it challenging for the ECM to perform correct mass flow measurement, causing tons of technical issues for the throttle body.

How to Test Mass Air Flow Sensor?

How to Test Mass Air Flow Sensor

Testing a MAF involves two smaller steps: checking its power feed and voltage signals. The section below will detail how to perform both self-test ranges quickly and efficiently. 

Test Its Power Feed

Step 1. Pop open the hood. Next, unplug the electrical connector of your MAF sensor. 

Step 2. Set its DMM (digital multimeters) to 19 or 20 volts auto-range or DC. Once done, connect the red lead of your meter to the connector’s B+ terminal (which leads to the car computer). If necessary, consult the repair manual for wire identifications.

Step 3. Connect the black lead of your meter to the (-) ground pins on sensor connectors. Next, swap the automobile ignition switches to “On”, but do not start your engine yet. 

Step 4. The voltage should be about 10 volts or at least close to that number. If not, that means your circuit’s power side is struggling.

Test Its Voltage Signal

Step 1. Switch the ignition key to “Off,” then plug the electrical connector of your MAF sensor in.

After that, black probe the (+) wire with the red lead of your meter – and the (-) one with the black lead. Ensure all the leads are kept far apart from all moving components within your engine.

Step 2. Engage your car’s parking brake, setting the automatic transmission signals to Neutral/Manual or Park/Automatic. 

Now kick start the engine before letting it enter rough idling sessions for a few minutes. The registered meter should be 0.5 – 0.7 volts (this estimation can be a bit higher for some models’ initial idle voltage). 

Step 3. Tap your MAF sensors and electrical connectors lightly – using a wrench or screwdriver’s handle. Wiggle the wire a little. 

At this point, the voltage outputs should still be steady. If you notice any engine stalling, surges, misfires, or fluctuations, that might be due to wobbly electrical connections that need replacements. 

Step 4. Increase the engine speed to 2500-3500 RPM and check the MAF’s output signal. It’s supposed to glide smoothly from 1.5 to 3 volts.

And what if your MAF sensor reading suffers from erratic performances – or the output voltage looks slower than usual? 

Chances are your car’s sensing elements or hot wires are contaminated/dirty, which implies bad relay and self-cleaning circuits. Sensor cleaners will be required under these circumstances.

FAQs

(Source: Wiki). 

1. Can Cars Still Operate Without MAF Sensors?

We don’t understand why such a question is even raised in the first place, but our answer is NO. Without MAFs, how can your car calculate its needed engine fuel pressure? 

The consequence is the vehicle running either too rich (excessive fuel and vacuum leaks) or too lean (insufficient fuel).

2. How Long Do MAFs Last?

They are designed for lifetime operation, with no need for scheduled replacement sessions. But, of course, natural tears and wear are inevitable, so once you spot a faulty sensor circuit, it’s time to swap that bad MAF sensor element with newer ones.

It’s best to change it every 80,000 miles or 150,00 miles for the optimal performance.

Keep our guide in mind and take actions after changing mass air flow sensor to ensure it is always at its peak condition!

3. What Are Some Signs Of A Bad MAF?

Listed below are some red flags of a faulty MAF:

  • There is black smoke from the exhaust pipe
  • The Check Engine light turns on
  • It’s difficult to crank up the engine 
  • The engine stalls after starting
  • There is a delay in acceleration
  • Your car shows a decrease in fuel efficiency
  • You experience rough idle

Once you tick at least one of these boxes, follow our guide above to test the part.

Conclusion

How to test mass air flow sensor signals? Bryan’s Garage believes this insightful article has covered all relevant aspects and advice.

We understand if certain confusion about air flow sensor failure might still linger for novices. In that case, feel free to drop in our inbox, which is open 24/7!

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