Top 5 Problems GMC Yukon SUV 4th Gen 2015-20

Hey, friends, it's Len here from 1A Auto. Today, we have another top problems video for you. This one's on a Gen 4 GMC Yukon. Let's get started.

Okay, friends. So, you know me, one of the first things that I always like to talk about in my videos is a safety issue. On this particular vehicle, there tends to be an issue with braking, which, of course, is a major safety issue. The symptoms that you might find with this braking issue would be basically the loss of vacuum pressure to help assist with your braking. Essentially, what I mean is when you go to step on the brakes so you can come to a stop or even slow, the brake pedal doesn't have that nice little cushy feeling to it and it doesn't slow down the vehicle the way that it should. Instead, you have to apply extra pressure with your foot to that pedal and hope that it, kind of, stops the vehicle but it's gonna, kind of, feel like you have manual braking like maybe back in the day with those antique cars.

So, obviously, not being able to stop or even slow down the way that you feel like you should is going to be a major big issue and, of course, that's one of the symptoms. With that said, the cause for this symptom would typically be an issue with the vacuum pressure that's supposed to be going to the booster, which is located right behind your master cylinder on your firewall. Overall, the booster is going to work with vacuum. It needs to have vacuum pressure to it so that way there, when you step on the brake, it's going to give it an extra assist and you don't have to press as hard, but the vehicle will want to stop like it should. If it's not receiving the proper amount of vacuum, well, you're going to have to press extra hard. So, let's talk a little bit more about that.

Now, looking along the driver side front of the engine, you're going to see this little pump right here, and it's belt-driven, okay? The pump right there is supposed to be a vacuum pump and it applies vacuum pressure right up through this line right here, and then, of course, it goes to that vacuum booster, which is attached to your firewall down at the end of there. Typically, what goes wrong with these pumps is more of an internal failure rather than an external failure. So, I'm not trying to talk about the belt or anything like that. That's more of a maintenance item. But the pump itself is something that tends to break down fairly frequently, and it definitely doesn't last as long as what it should, or at least as long as what is designed to do.

So, now with that said, the pump is the most common cause for this particular issue, but you can't rule out anything else. Essentially, you have this line right here, which has a connection point where it connects onto the pump down there. If that has a leak with one of the O-rings, obviously, you're gonna lose vacuum. Follow that line right up though, it's gonna come up to your brake booster right up here. If you happen to notice that this is loose and it wiggles around or even pops right out of there, obviously, there's an issue with the seal right here. Once again, you're going to have no vacuum to power up this booster, and you're going to have a super hard brake pedal.

Aside from that, people might say that you might need to replace the master cylinder or even the brake booster if you're having this issue. In all actuality, it's probably not the real cause of what's going on here. I would start with that pump and/or checking for vacuum right there. But some things that you might happen to find with the master cylinder or even the brake booster that might make you think that you'd want to replace it might be something such as the fact that you're looking at the master cylinder where it connects to the brake booster, and you can see that there's fluid all coming down along the bottom and it's eating away the paint.

That's not very common on this, but it is something that's common with master cylinders when they go bad. If that happens, that means that the seal on the backside of the master cylinder is leaking. More than likely, it's also leaking into the brake booster. In which case, you have brake fluid inside there, you're going to need to service that/probably replace it at the same time you'd replace the master cylinder and, of course, check to make sure you have vacuum as you should.

"Hey, buddy, pull over. You got a light out." Problem number two on this particular vehicle is it tends to be one of your tail lamps or maybe even both tend to go out for some reason. Usually, when it happens, it's more than likely going to be all the bulbs in it in exception of just the reverse light for some reason. Let's take a quick peek behind the lens. So, the lamp itself is supposed to be LEDs in there. So, it's going to have a nice circuit board on the backside. You're gonna, of course, have your wiring on both here. You've got your reverse light, and then this is for the rest of the tail lamp assembly. If you were to just go ahead and disconnect it and take a peek, what you might tend to notice is either this has melted a little bit.

You might see some black areas where those little prongs are supposed to go into or you might even see some funny colors such as corrosion. If that's the case, you'd have to replace the pigtail, but that's not always the most common cause. Generally, of course, you'd want to try to peel back this layer right here and expose the wires inside so you can check to make sure they're not damaged or overheated in any way, especially if you happen to notice that there's an issue up here. Aside from that, if you were to look right here, you want to check for corrosion or damage right there as well. Right in behind this area right here is where there's going to be a nice big circuit board inside there, and that's what's going to control the lights so they know when to turn on or off or turn, you know, directional left or right, whatever the case may be.

The circuit board inside can tend to get contaminated by something or even overheat. When I say contaminated, I essentially mean that it might get moisture inside there. In which case, it's going to build up corrosion. If it builds up corrosion, it's going to cost restrictions and it might even mess up the circuit board completely. If it overheats, well, you're going to have pretty much the same issue where the circuit board's just toast and then, of course, that's going to be an issue. Overall, if you were to remove the screws coming along the sides here, you've got a bunch of them going around, you could theoretically take this right apart and take a look at the circuit board that's on the inside there.

If you were to go to the dealer, they're going to tell you that you're just going to want to go ahead and replace this. That's probably going to be the easiest thing. It's probably going to cost you over $700, but we're not going to get into that. Me personally, if I thought that I was going to have to replace it for over $700, I would try anything I could to try to fix it first. If that's the case, like I said, remove your screws, take a look at that circuit board. If it's something that looks like it could be cleaned up or even fixed in any way, obviously, that's the way to go. Go ahead and plug it all back in, test it, if it works fine, great. If it doesn't, well, then you're going to have to replace the unit itself.

Now, the third problem on this particular vehicle comes down to the fuel injector O-rings. Some of the symptoms that you might find if you're having an issue with your fuel injector O-ring, whether it's the top or the bottom, might be, of course, a fuel smell coming from underneath your hood. You might also notice that your engine kind of runs a little funny. That would technically be considered a misfire. If you have a misfire, you're, kind of, sitting inside your vehicle, potentially sitting idling, and you're gonna feel like a little shutter, ooh, ooh. That's not necessarily because the engine is cold or anything like that and it's just shivering, it's actually got a little bit of a misfire because it's not receiving the proper amount of fuel to mix in with the air inside the combustion chamber.

With that said, if you're getting a misfire, more than likely, you're going to get a check engine light code. The code might come up as a P0300, which would mean a random misfire code, or it might come up with something such as like a P0301, P0302, so on. If you have P0301, that means it's a cylinder one misfire. Like I said, if you have an issue with this right here, you're not gonna have enough fuel pressure getting into that fuel rail, getting fed into that combustion chamber so, of course, you're going to have a running condition.

So, some of the fixes for this would be, of course, if you can smell that you have fuel coming from underneath the hood area, more than likely, it's going to be this cause. If you just find that you have a misfire and you're sure that your spark plugs and your coil and everything are fine, you might actually have a fuel pressure issue. In which case, you'd probably want to either hook up a scanner and you can usually test it that way or, of course, you can use a fuel pressure gauge. Essentially, what that's going to do though, is let you know if you have enough pressure coming from the pump leading up to here. But if you have an issue up here with one of these injectors, you're probably really not going to notice it so much until you actually take a nice peek or even just, kind of, sniff around to see where potentially the fuel smell could be coming from.

Looking towards the driver side rear of the engine, you can see where your fuel line comes in, and then it goes in and gets buried underneath your intake. That's pretty much where all your fuel injectors are going to be. So, if that's the case, obviously, they're not going to be very apparent to be able to see, you're gonna have to take apart the upper part of your engine here and get that intake off of there. If you did happen to find that you had an issue with one of your fuel injector O-rings, of course, you'd want to go ahead and replace those. You can usually get them as a kit with the upper and lower, and if you're doing one injector, well, why not just do them all?

So, now, our fourth problem on this vehicle continues on with the fuel injectors. And it's not necessarily an issue with the fuel injector itself, it's more of an issue with black smoke coming from your tailpipe and it has to do with the fuel injectors. So, symptoms that you might find other than just the black smoke coming from your tailpipe, like I said before, might be something such as like maybe a misfire-type feeling or a little bit of a shutter, kind of like what we were talking about with the leak from the seal right here. But this is kind of going in the opposite direction. The reason why this is happening is actually because the vehicle is trying to pump in more fuel. It basically is doubling up the amount of fuel getting pumped into each cylinder, so it's gonna run rich. As it runs rich, it's going to heat up that catalytic converter faster for you, and then, of course, it's going to help out with emissions and, overall, it should actually help with fuel economy in the long run.

But, of course, that can be worrisome, especially if you're driving around in a newer vehicle, you definitely don't want to see smoke coming out of your tailpipe and you definitely don't want to feel like you have a misfire. Something to think about though, is that this is a very common thing, it's supposed to do it, and it's really only gonna happen when the engine is very cold, like at its coldest point. Maybe it's a nice winter day, you come out in the morning and you start it up, it's trying to warm up at that point. That's the only time that you really should be feeling this and it should only last for approximately 60 seconds.

Now, for our fifth problem on this particular vehicle involves our seatbelt retention right here. What you might happen to notice is you're sitting in your vehicle and you're buckled up, of course, as you should be, you go to get out and for some reason, the seatbelt either just kind of slowly makes its way back in or maybe it doesn't even at all, and then you're left with this thing just, kind of, flapping around. The problem itself would actually generally stem from outside contaminants, such as maybe you're wearing some sunscreen or maybe a little bit of makeup, or maybe you're wearing greasy gloves and you're pulling around on this, which I changed my before this, just so you know.

With that said, if you were to look up inside here where the seatbelt rests on and it's supposed to right across, you might see a little bit of gunk or even film. That's gonna, kind of, make this so it, kind of, just, kind of, moseys its way along here and it's not flowing as smoothly as it should. So, what you actually need to do is go ahead and clean this down. When I say clean it down though, I don't mean using anything like maybe a parts cleaner or anything like that, something that's harsh and has harsh chemicals inside of it, because not only could you damage this right here, which, of course, is metal so it's pretty unlikely, but you might damage the belt itself, which, of course, would be a major safety issue. Other than that, when you do go to clean this, you don't want to use something such as sandpaper, of course. If you do that, you could scuff up this area, which, of course, is gonna put little tiny tears in your seatbelt. Over time, that's going to cause wear and this needs to be as strong as possible.

Some people might use a little bit of velcro, like a strip of it, and put it inside here and just try to work it back and forth using the seatbelt as well to use some pressure. I like to use a little rag. I'll just, kind of, weasel it inside there in between the seatbelt and the D-ring itself and just try to clean it up. I like to see how much gunk comes off of there and you might be a little surprised what you see. Once you clean it up, go ahead and give it a test, it should come right up like this. And that's perfect. Of course, if it doesn't, continue cleaning it. You definitely don't want to leave it so it's not functioning properly because, of course, that could mess up the internals where the actual tension's supposed to be. If it doesn't sense that this is doing its job right, well, you might come down with other issues as well.

Okay, friends, so that's pretty much all I've got for you for top problems on this particular vehicle. In all honesty, it was kind of hard to come up with even those because it's a great vehicle. Overall, I hope you liked the video. If you did, go ahead and smash on the like button for me because it would mean the world. Leave me a comment because I always love to hear from you. And subscribe and ring the bell, that way there, you can be kept up with all of our latest content. Thanks.