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What Does a Mass Air Flow Sensor Do in a Car Truck SUV

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What Does a Mass Air Flow Sensor Do in a Car Truck SUV

Created on: 2020-07-07

This video teaches you what a mass air flow sensor is, the job it performs, and what to do if it's not working correctly!

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In today's video, I want to talk to you about this little part right here. It might seem small to you, but it's going to make all the difference in the runnability of your vehicle. Let's talk about it.

Hey, friends, it's Len here from 1A Auto. Today, we're going to be talking to you about mass air flow sensors. They come in all shapes and sizes. Some might seem very small, others seem like they come in a big old unit that looks like this, but they pretty much do the same exact thing, and let's talk about what they do. Now, just to say, this isn't necessarily a diag video, this is more of an overview video. What a mass airflow sensor is supposed to do is it's supposed to measure the amount of volume and density of the air getting drawn into your engine. It's going to send out a little signal that goes out to the car's computer, and it's going to say, you need to match this amount of fuel to this amount of air so that way there the vehicle can run efficiently. Now, the accuracy of your mass air flow sensor is going to be critical to making sure that your engine runs properly. If for some reason it's dirty in any way or even damaged, it's going to cause an issue with the runnability of your vehicle like I said before.

Now, in most modern-day fuel-injected vehicles, they're going to have a mass air flow sensor, and it's going to be located someplace close to the air filter. Somewhere generally on the air intake system. So, on this one right here, you can see it right there. If you were to move right along here, we're looking, I don't necessarily see one on top, but if I was to pull this out, I can see some wiring and then look right inside and we can see the mass air flow sensor there. So, as you can tell, like I said, most vehicles, the mass air flow sensor is going to be located somewhere on the air intake, which is the area that the air is going to get pulled into the engine from the air filter.

Now, here's just some of the mass air flow sensors that we have from some of the vehicles we have here. What you're going to notice is that they have a lot of different shapes and sizes and differences overall. Some mass air flow sensors are going to have an air temp sensor located within them. So, it's going to kind of be like a multi-sensor, but overall, they're going to do the same basic thing, which would be measuring the amount of volume and density of air getting drawn into the engine. On the inside of the mass air flow sensor, what you're overall going to see is right here you can see that there's like a little piton, that comes up in the center there. That's actually the measuring device. And if you were to look at any one of these, you're probably going to see about the same.

So, some of the symptoms of when your mass air flow sensor would go bad is maybe you notice your vehicle doesn't want to start very well, maybe you notice that your fuel economy went way down. Of course, that's a boo. Other things you might notice is your vehicle doesn't run right overall. Maybe it skips a little bit, maybe it's hesitant, you step on the gas, you want it to go, it just doesn't because it doesn't sense how much air is getting pulled through the intake to mix with the amount of fuel, so your vehicle just doesn't really know what's going on. And you might also notice you get a check engine light that comes on on your dash. Of course, that's no good. The code that's probably going to come up with this is going to be a P0101. What that's going to stand for is that the sensor is saying that things are out of range. Whether it's getting too much air or not enough air, the sensor in there is probably a little bit dirty or maybe even broken and it's not communicating right with the vehicle.

Before we go ahead and condemn that mass air flow sensor and say maybe it needs replacement, or even just a basic cleaning, we have to think about some other things. You have to remember you have an air filter inside your vehicle, of course. The air is going to get drawn through the lower intake area, through the air filter, which should filter out all the particles, come out through the other side. At which point, it's going to be sensed how much air flow is getting pulled through the air intake system, it's going to go through this mass air flow sensor. If for some reason your air filter is dirty, obviously, the mass air flow sensor is going to sense a restriction, and it's going to say, "Hey, I'm not getting enough air. There's going to be a problem." So, you're going to want to check that out first. Make sure your air filter's good. There are some other things that you'd want to check for though. Maybe you have an air intake leak someplace like a vacuum leak. Maybe you checked that air filter, it looked great, or maybe it was dirty. You went ahead and replaced it, you put it back together. That's great. Maybe for some reason when you tightened up that clamp, the hose wasn't sitting on there perfectly. So, if you have a loose clamp or maybe you have something that wasn't connected properly, of course, there's going to be air that's getting pulled through that shouldn't be pulled through at that particular moment, and the sensor is going to read that as well, especially if you have an air leak after the mass air flow sensor. So, let's assume you have your air filter, the tube, mass air flow sensor, tube, and then your engine. Somewhere between the tube and the engine down here, for some reason it's not connected or maybe a hose is disconnected, now you have unmetered air getting drawn into the engine, so your mass air flow sensor is going to throw up a code saying, "I don't know what the heck is going on."

Checking for places of air leaks. Of course, you'd check the box where the air filter is going to be. Make sure it's secure. Check your clamps, give them a nice wiggle. Check, of course, the sensors, make sure there's no leaks. We'll wiggle everything around. That shouldn't move around like that. That's not going to make a good seal. Make sure everything's nice and snug. Feeling along. No, what's this? That's going to be an area where unfiltered and unmetered air gets right in. That's very bad.

Now, just to let you know, the mass air flow sensor doesn't only communicate with the car's computer, it's also going to communicate with the car's air intake temperature sensor. And that's located in that same hose that we were talking about before, whether it's part of the mass air flow sensor or it's a separate unit itself. The reason why it needs to communicate directly with the intake air temperature sensor is because it needs to know exactly the temperature of the air getting drawn through the mass air flow sensor as it's sensing. The reason for that is because cold air is going to be more dense than warm air. So, if it knows what temperature the air is, it can kind of do the calculations ahead of time before it sends it ahead to the ECU or car's computer. There is a little bit of fact-checking involved and that's done by the O2 sensors, which are located down on the exhaust. Now, for your vehicle to run the most efficient, it needs to have 14.7 parts of air compared to 1 part of fuel mixed as it's getting put into the vehicle for combustion. If for some reason your O2 sensor, which like I said, is located on the exhaust, comes back saying, "Whoa, we have a lean condition here," which means that you're getting too much air and not enough fuel, it's going to go ahead and say, "Hey, computer, you mind giving me a little bit more fuel over here so we can get that proper combustion?" It's going to say, "Yeah, sure, buddy." Dump it right in there. Next thing you know, what's really happening is you're creating a rich condition, which of course is going to cause issues down the line, specifically being your catalytic converter. And, of course, if the O2 sensor is telling the computer there's a rich condition, the response is going to be the opposite.

Now, like I said, this video isn't necessarily about diagnosing the mass air flow sensor. But if it was, you can go ahead and try to use one of these scanners right here if you got a couple thousand bucks laying around. These are great because you can graph it. You can check how much voltage is going through at different RPMs. So, that's, of course, super. If you don't necessarily have a couple thousand bucks laying around, you can get yourself one of these right here, it's a little multimeter. You can find them pretty much anywhere, especially And you can check out the voltage and everything like that, and that'll lead you down the right way. Like I said, this isn't a diagnostic video, so I'm not going to get into specifics about this. But if you're just hanging out in the driveway and you're trying to figure out what's going on, what I would actually do is, of course, would make sure that the vehicle off. I would unplug that mass air flow sensor, dislodge it from the air intake system there, and take a peek. If it looks like it's dirty, I would probably try to clean it. And when I say clean it, I mean you need to use specific cleaner for that. You don't want to just go ahead and use parts cleaner or something like that because it could leave a residue. When you're cleaning out the little filament on the mass air flow sensor, you need to use a specific detergent that says mass air flow sensor cleaner only, okay? The reason for that is because, like I said, you don't want to leave any oils or anything like that on the little sensing unit.

Okay, friends, so real quick, we're going to show you how to clean this mass air flow sensor. First thing that I want to talk about, make sure you have eyes and hand protection. Super important, okay? We're going to be dealing with chemicals. We're going to be using a mass air flow sensor cleaner. Like I said, we're not going to go ahead and use the multipurpose solvent or anything like that. When we're cleaning this, we want to try to clean that little bobble that's located right inside there. It's kind of hard to see, but when we clean this down, when we're using our spray, we want to make sure that we're not going directly against it, pushing the hose or anything like that near it. Try to come from a distance. Of course, make sure you go into a nice recycling bin here. We're going to go just like this. You can see it changing colors. That's the actual color that it's supposed to be. I'm going nice and light here, I'm not blasting directly at it. It's kinda more like indirectly. I'll go ahead and get the backside too. That's great. When you're cleaning these, it's important not to necessarily clean them upside down. Like if I was to spin this upside down, there's a possibility I can get fluid or cleaner up inside the mass air flow sensor itself to where the circuit board is and that could be an issue. Other things to think about when you're cleaning these is just because you just spray this down, maybe you want to try to dry it off, right? You're going to grab your little blowgun here. Spray, spray, spray. Well, there's a lot of pressure that's going to come out of this blow gun, and it could potentially damage this. This is a very sensitive piece of equipment right here. So, you definitely do not want to spray this with compressed air. Other things to think about when you're cleaning it, don't go ahead and use a brush and try to scrub it. If you can't get off the crud that's on there with just using the mass air flow sensor spray, well, it's probably too dirty and it's probably worn anyway. With that said, I let this dry, I'm taking a nice peek. In all honesty, I think I might give it another quick blast real quick, but overall, I don't see any potential damage to this. I don't see any reason why cleaning it down wouldn't fix the issue.

At this point, you're probably wondering, why did my mass air flow sensor go bad? Like I said, this isn't a diagnosis, but couple of things that I would think about is the condition of your air filter. If your air filter is very clogged or even you tried blowing it out with maybe an air gun of some sort and you spread those fibers, there's going to be particles that get pulled by and they're going to collect right on your mass air flow sensor. If you have debris or any type of accumulation of stuff on the mass air flow sensor, it's going to cause an issue. Other things that might happen is it has an electronic circuit board that's going to be located inside with, of course, a connector here. If moisture makes its way inside of here and contaminates the circuit board that's in there, maybe causes corrosion or something like that, it's going to cause resistance, which, of course, would cause an issue with the computer trying to figure out what's going on with the mass air flow sensor. Other things that it might be is maybe you just tried cleaning it, you used a brush like I said you shouldn't, maybe you used some parts cleaner, or even maybe you just stuck a little screwdriver in there and you're trying to clean it up for some reason. One last thing that I could think of is just if you drop the thing. Maybe for some reason it doesn't look like it's very broken, it's not cracked or anything, what's the big deal? I go ahead and install it into the vehicle, well, what did I do on the inside here? I probably busted something up and more than likely this isn't going to communicate properly anymore.

So, now, if you're wondering if the importance of cleaning/maintaining your mass air flow sensor is a safety issue, I would say minimally, only because, well, if you have some sort of misfire or sluggishness coming from your engine, obviously, that could be a safety issue. But overall, would I say that maintaining and cleaning/replacing your mass air flow sensor as needed is that important for the engine? Yeah, of course, it's super important because if your engine doesn't know how much air it's receiving and it's mixing too much fuel or not enough fuel, you could potentially damage your catalytic converter or other mechanical parts of your engine.

Okay. So, let's say you checked everything that we went over in this video. You did a little bit of research and you figured out how to diagnose what's going on. Maybe for some reason it's still coming up saying that you're having an issue with the mass air flow sensor. At that point, what I would do is go to and order myself a new one.

Now, something that's super important to remember is whether you just cleaned or even just replaced your mass air flow sensor, you're going to want to relieve your negative battery terminal from the battery. Leave it off for approximately 15 to 20 minutes. That way there, your vehicle can reset its parameters inside of the ECU or brain of the car. Something that's important to remember with that though, is if you take off the negative battery terminal you take a risk of resetting other things such as maybe your radio stations.

Okay, friends, so we tried to give you a general overview of a mass air flow sensor on your vehicle. Hopefully, you learned a little something along the way. If you got something to say, leave it in the comment section below, because I'd love to hear from you. If you like the video, please make sure you smash on the like button for me, it would mean the world. While you're at it, why don't you go ahead and subscribe and ring the bell, that way there you can be kept up with all of our latest content. Thanks.

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