How to Replace Knock Sensor Harness 2000-06 GMC Yukon

Because we're gonna have to disconnect the fuel system, we wanna take the pressure out of the fuel system. Just take this relay out right here. Find the fuel pump relay, grab that, take that out. And then you can try to start the vehicle. Our vehicle doesn't run right now. So if you crank the vehicle and then it dies, the fuel system should be unpressurized. Now I'm gonna disconnect the battery. Use an 8-millimeter wrench. Loosen up the negative side terminal and just set that wire aside. Take this cover off. Use an 8-millimeter socket and slide it off. Take the snorkel off, this little retainer right here. Just use a trim tool. Slide that off. Then loosen up the worm clamp. Use an 8-millimeter socket or you can use a straight blade screwdriver. Same with this one. Grab the snorkel, slide it back, and slide it out. Take this nut off right here. Use a 10-millimeter socket and then these 2 10-millimeter bolts, and then that one. And take this cover off. And we're gonna disconnect the connectors. Disconnect that one right there. It's off the purge solenoid. Disconnect the alternator connector right here, slide under the lock and pull it out. And this connector right here and the MAP sensor as well. Disconnect that. And I'm just gonna use a bungee cord to just keep the wires out of the way. Just wrap it around the wiper arm.

This wire connector right here, just unattach that from the intake, set that aside. Now we have to disconnect all the fuel injectors. There is a lock on them. This one doesn't have that lock on it, but you pull back on the lock and then you push down on that little lock tab and then slide the connector out. This one does have the lock, so the lock, you just grab the lock and just slide it up just a little bit, and then you should be able to push on the connector. Sometimes it's easier to slide whole lock out. This is how the lock works. So when it's locked in there, this is all the way down. Slide this out. You should be able to slide this out a little bit. You don't have to slide it out that much. Okay. That's how it's locked. Should be able to slide it out to there and then push down on the tab and release it. But like I said, sometimes it's easier just to slide this whole thing out, push it down, slide it out. Do that for all eight of them. All right. Disconnect the connector to the throttle body and just pull back on this little lock. Once it's back that far, push down on the tab, disconnect it. Now you could leave the throttle body attached. There's just coolant hoses that go to it. So you can either take those hoses off and just leave that all attached, take it all off on the intake or take the throttle body off. I'm gonna use a 10-millimeter socket. Take these nuts off.

And sometimes the stud comes out completely. That's okay. Let's get the other two out. Now, you wanna be careful with this. It is sensitive. You don't wanna drop it. And slide this hose out of the way over here. And disconnect this hose right here. This goes to the valve cover. You can either disconnect it down here or up here. And it's been on there for a long time, so it's kind of hard to get it loose. Just try to twist it back and forth. Screwdriver or a trim tool or something, just try to push on it. It should probably be replaced. The rubber is very dry. Just try not to crack this little port. There we go. Yeah. See the hose is starting to rip already. Move that to the side. Disconnect this EVAP line. Might need a screwdriver or something to push on the tab. It slides up. Now, when we take the intake off, since I'm not pulling the injector rail up, we're just gonna have to feed this through there. So just keep that in mind. And back here, disconnect this line that goes to the valve cover. Just pop that up. You could disconnect it up here if you wanted to and just put that out of the way.

Now, if you weren't able to bleed the pressure off the fuel system like I showed you earlier, taking the relay out and cranking it, just take the cap off right here. Take some rags and a screwdriver and you're just gonna push on this Schrader valve. Just be careful. It's a good idea to wear safety glasses while you're doing this. And just release the pressure. There wasn't a lot of pressure in this one, but sometimes they spray pretty good. It's good. Put the cap back on so I don't lose it. Now we'll disconnect the fuel line, just pull this lock off, and just slide it up and then pull it out. You're gonna need a special fuel line release tool. Just slide this over the pipe, pull the line forward, and then push the tool into the line. Once the tool is in the right spot, you should be able to pull the line back. Just like that. Pop it off.

Now wer're gonna take the intake bolts out. There's one there, one there, one there, and then there's two in the back on this side, on the opposite side. There's two in the front, one in the middle, and then two further back. So there's 5 per side, 10 in total. I'm gonna use an 8-millimeter socket. It helps to use a wobble socket or a swivel socket. And it's a good idea not to use an electric tool with the gas being out. You don't wanna cause any sparks. So I'm just gonna use an air tool. All right. All those bolts are loose. Just grab the intake, slide it up. Just remember this hose has to go underneath the fuel rail over here. And just slide it through there. Like that. Just be careful, it is plastic. You don't wanna crack it. And then when you go back in, you're gonna have to feed that through there again and slide it out.

So it's pretty dirty under here. I wanna clean some of this up. I don't want any of this stuff to fall into the intake ports. What you could do is put a rag in each one of those ports and then clean it all up if that's what you wanna do or just be careful. And you don't really wanna use a electric vacuum on this because the potential of getting some of the fuel in there and then catching the vacuum on fire. So just be careful. All right. So I put rags in all the ports. I just need to remember to take those out when I go to put the intake back on. Just use a blowgun. Just try to blow most of this away. And we're gonna pull this little cover up right here. Just use a trim tool or a screwdriver and just slide it up. It should slide on the wire. And just be careful. There we go. Disconnect the connector. It's kind of hard to do with your fingers. Might be easier with some needle nose pliers. And disconnect the connector. When you squeeze that, that releases the locks. And just do the same with the back one. There we go.

And the harness is disconnected. And just pull it away. And take the new connector and just lock it in place. Do the same on the back one. That's good. Now we can push these seals down. That's good. Do the same on this one. Perfect. Now you wanna run the harness this way. Just have it sitting back here so when we go to put the intake back on we can plug it right back in. Before I put the intake on, I just wanna take some brake parts cleaner and just clean the surfaces where the intake gasket is gonna sit. You don't have to clean all this up crystal clear or anything, but just where the gasket is gonna sit, make sure that's nice and clean. You can gently use a razor blade to clean some of this up. Just be careful. You don't wanna gouge the metal or you don't wanna cut yourself.

We'll take the old gaskets off. There's a little clip right here. There's another clip right here and then another one on the bottom. Take those off. Try not to tip the intake completely upside down. Just try to keep it on its side so none of the dirt goes into the ports and then just take a little rag and some brake parts cleaner and just wipe around the intake. And take the new gasket, just line it up, and click it into place right there, right there, and on the bottom. Just make sure that looks good. Do the same on the other one.
Don't forget to take these rags out. You can check all the ports. Just look down and make sure there's nothing that went in there. You could always spray a little compressed air. Now when we go to put the intake back on, we have to slide this back through the fuel rail. You could always disconnect it right here and just put this on the intake and then reconnect it down there if that makes it easier for you. And take the intake. This line is gonna go through right here. And just line it up. Watch this line, push that back there, and just wiggle the intake a little bit. Make sure you didn't crush any of the wires. Make sure this wire is accessible. It goes to the knock sensors. We can actually put this...just attach that right there right now so you don't lose that and get all the bolts started. Now I'm just gonna snug them down first. There is a sequence to tighten these up, but I'll snug them down first and then we'll do the torquing and the sequence after.

So, number one, I'm gonna torque this bolt to 44-inch-pounds, and that's the center one on the passenger side. That's number one. Number two is gonna be the center one on the driver side. Number three is gonna be on the driver side, the next one back. So number four from the middle one, the next one forward. Number five from the middle one, back one. Number six, on the driver side from the middle, forward one. Number seven is the next one forward. Number eight is the passenger side rear one. Number nine is the driver side rear. And number 10 is passenger side front one. So that was all the first pass. Now you're gonna do the same sequence and you're gonna change your torque wrench to 88-inch-pounds. And do the same exact sequence. Now we'll hook up the fuel line, line that up, lock it in place. Make sure that's good. Make sure you put this lock on, just slides on, and then locks down. It's just gonna prevent it from coming off.

Now hookup this line or hose right here. It goes to the valve cover. And hook this line up over here. Ours is split. This should be replaced, but it'll work for now. And the EVAP line, just make sure it locks in place. And that's good. Now check your throttle body gasket. If it's crushed, normally you have to replace it every time, but if it looks okay, you can probably try to reuse it. This one looks good. And take the studs or just the nuts if the studs didn't come out. Put those back on. And then I'm gonna torque these to 89-inch-pounds. Now reposition that coolant hose, and those clamps, take the electrical connector, line it up, lock it in place, push down on the lock. That's good. Now we wanna plug these injectors back in. Just take the locks, reposition the locks how those go. And plug those in. Make sure they're secure. Do the same with the other seven. Let's disconnect this bungee cord and run the wires same way they came out. This bracket's gonna go right here and those wires are gonna go like that. We can connect this connector right here. That goes to the knock sensor wire right there. And then this connector is gonna go to the MAP sensor in the back right there.

Now take this bracket, line that up. And take the bolts, get those all started. Put the nut on this bracket right here. That's good. Take these connectors, plug in the alternator. And this purge valve, plug that one in. And take the snorkel, line it up over the intake or the throttle body. Line this bracket up right here and over the airbox or mass airflow sensor. Tighten up this worm clamp right here. Just snug. And the same right here. Take the cover, line the cover up in the back, and get the bolt started, and tighten it up. Snug. Now let's reconnect the battery. Put the negative terminal on and snug it up. And then wiggle it, make sure it's not loose, and you're good to go.