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Customer Customer States Mechanic Fails Engine Transmission Gas Diesel off road race 4x4 street car daily driver scam dealership dealer technician how to

Say p 300 one more time. Give me a trouble code p300 just one more time. Hello there everybody! Good day to you! Welcome back Check this out. We have dueling Silverados We got the dually Silverado and the non-dually Silverado This is a 2005 2500 HD I Believe it's four wheel drive I think it's a Gasser that tells me it's gonna have the six liter, uh, probably the Lq4 engine.

I've kind of got a list of uh, stuff that needs to be looked at and stuff that has already been looked at. Uh so I'm not sure what direction this video is going to go in, but I'm pretty sure I can uh come up with the ability to organize it. Let's see, we've got right at the get-go a change engine oil indicator Illuminator We've got the check engine light turned on. What do we have for some mileage? Not bad.

129 611 miles on the odometer. All right. So I'm taking a look at my list here. Um, looks like some of the leg where it's been done for me.

We've got a C code c0035 something indicating a left front wheel speed sensor fault. We'll take a peek at that. P0446 that's emissions. That's the fuel tank evaporative system.

Looks like the thing's got a misfire. That's the dreaded P300. I Understand, it's already had spark plugs and wires and ignition components installed, so that 300 is going to be fun to track down. Uh, looks like the AC system is a little bit underperforming when it's hot outside.

Yeah, it's it's that time of year. It's been so hot lately that no matter what kind of AC you have and no matter how good your system is, they're just not making the cold that people are used to like. Once we get into those temperatures above like 9, 94, 95 then your vent temp is is going to suffer because they just don't have the cooling capacity to keep up with the with this current heat wave that we all seem to be living in. In fact, I hear it was so intense that there were certain model of aircraft that were not uh, they were not able to land out west in like Los Angeles uh due to the heat Factor simply because those aircraft did not meet their performance numbers to make a safe landing.

so they had to use like Boeing 757s or something like that. Very very strange phenomenon. Too much heat stuff doesn't work Anyways, that's a tangent that is, uh, not conducive with the flow of this video. So we're going to abandon the uh, the airplane topic and get back to our Silverado right here.

I'm gonna go ahead and back this thing in uh, in my middle stall I Don't know if I want to put this super huge heavy truck on that new lift just yet I Don't know if I trust it that much so we're gonna go in the middle. uh, not the big rack because Troy is in the corner right now pulling machinery off the wall and uh, cleaning and scrubbing all of that nasty dinge stuff that was on the side of the walls over there. And he's taking some green scrubby pads and scrubbing off all of the uh, the nasty that has been accumulating and caked on the walls in the shop. All right, right, backing up, backing it in, getting her lined up.
We'll get this thing, uh, near the, uh, the approximate lift location, then I'm going to bust out the scan tool, see what these codes are about. We're going to formulate a plan of repair and uh, and get this thing started. So stay tuned because this is gonna be a very good video. One thing that they mentioned is that going between like reverse and drive, they hear a clunk down below at the drivetrain.

Oh yeah, it's doing it all right. Yeah, let's go down below real quick and see if we can't see what that clunky noise is. We'll check that one off the list. Hey darling, can I borrow you over here? I Need your foot? What can I borrow you? I Need your foot? Yeah.

Come here babe. Okay, so what I need you to do real quick? Like, um, hop in here, keep your foot on the brake and switch between reverse and drive. Do you hear that clunk down there? Yes, we need to recreate that clunk. Okay, and I'm gonna crawl down below, so don't run me over.

Okay, okay, thank you darling. All right. Go ahead. Go between reverse and drive.

Huh? Do it again. I Hear it up front. Keep doing it. Crawl around.

Keep doing it. It's in the drive shaft. What is this? Keep doing it. Keep doing it up here.

Where is the sound located in the exhaust? Oh if I put my hand on it. Weird. Okay, so it sounds like it's in the drive shaft right now. We can see these U-joints are not moving around.

it's not loose U-joints and we hear the sound in the shaft. But that doesn't mean the shaft is making the sound. If I hold it. see that sound goes away by.

hang on to it again. Let's put some more pressure on it This way. there we go. see the sound goes away.

If I hang on to it. Hey Lauren put it in park. Too much slop. There's a little bit of play out back in the rear differential.

Also, see all that motion back there. That's actually kind of a lot. I'm sort of inclined to pull off that rear diff cover and take a look under it. Let's just go ahead and start from the rear end.

first. it's either in the rear or it's happening up here. Uh, in the tail shaft. All right.

babe. Put it in park. Let me get out of here. Nice shiny new lines.

Look at that. So it's definitely in the drivetrain. It's got something to do with the drive shaft. It's not the universal joints I need to dig myself out of here.

It's not the U-joint so it's got to be one of the other movie components. We're gonna check back in on that later after. I crawl out of this hole that I'm in. Oh my gosh stuck.

Hang on. Watch this. Cool. There we go.

That's where I just crawled out of. All right. Thank you darling. I will trade you seats or or I'll take your seat I Need my scan tool? All right Scanner, scanner, scanner.

Where are you? Oh I don't know where any of my stuff is I'm all discombobulated places Tore Up From the Floor Up But it is looking better though. Uh, to my eye. which is cool. That's a uh, that's a nicer environment.
Let's plug the skin tool on and in and on. Beep powering on. Yeah, that's another thing about a lot of shops is they they end up being gross and dingy and nasty and dark and dimly lit. and that creates a terrible environment that nobody wants to be in.

And I'm trying to undo that because this shop is sort of no exception. Okay, Scan Tool Auto ID has identified this truck as a four-wheel drive 05 Silverado six liter with the Lq4. That's the RPO code for the engine. Now the paper mentioned a C code for uh, something to do with the left front wheel speed sensor.

So let's pull up any lock, brakes, display codes and we'll see if that C code is present. That's a negative, not present. Let's go back to history see if it's logged in history somewhere. Left front wheel speed sensor Circuit fault.

Okay, so that's not a implausibility code meaning it. uh, it has a problem with the speed that's being registered. It is saying that it does not see anything on the circuit whatsoever. So let's just take a peek at our circuit.

here. we're at the left front. that's our wire, see how it's looking down a little farther below. I Got to stick my Noggin in here.

Wire looks good, so it's either got an open down, uh, down at the wheel speed sensor itself or we're getting bad connection at the connector or something like that I'd Be willing to bet that uh, you know, we're probably going to find out that the actual sensor itself is faulty and it's generating generating its open uh, open symptom while driving intermittently. Let's go into engine. We're going to verify that p300 and we can also verify that emissions trouble code. So let's get into our engine here: display codes.

If you're not everybody, we're not going to spend this entire video inside of the scan tool. Yep, there we go. P300 engine misfire and P0446 evap vent control. We will tackle the EVAP system later.

I Want to go after those misfires first. Okay, pulling up engine misfire data. Cylinders one through seven are showing zero current misfires. And if we look here in our history count, we've got what? 2100 on cylinder one cylinder 5's got 36 000 991.

We've got a couple 1600 and three misfires on cylinder number six. So so far predominantly we've got one five I'm sorry. So yeah. six and eight, One, five, six and eight.

Those are our misfire cylinders. So yeah, it's all over the place. All right. I've got it in Drive put on the brake I'm sort of power breaking it a little bit and we're looking for misfires.

Uh, to show up I'm looking at the current count and I I saw two of them show up I think on cylinder two, but they've they've subsided. Here we go. There's some five and six. Yeah, there's a couple that showed up.
one on cylinder number two. Yeah, so we're getting a few misfires. There's one on number one so that it seems to be happening as I D cell. Maybe let's blurp the throttle some.

Yeah, they're not happening while it's consistent. but if I let off and get back on the throttle, they like to show back up. Okay, I'm taking a look at the O2 sensors. Bank one and Bank two.

Uh, Upstream Before the cat, both sensors appear to be switching. Fuel trims also look pretty good. Scroll down to fuel trims I Saw a bank one. Short terms are hovering around zero.

Long term: Zero two Negative one. So fuel trims are also looking really good here. Our O2 sensors. So we got Bank One sensor one and we skip a graph and go to bank two Sensor one.

These are the Upstreams and both graphs appear to be switching and they are emulating each other. The frequency looks good and they are following each other regardless of throttle position. So I'm not seeing one of these sensors dropping out I'm not seeing it biased towards zero. You can see it bias towards 800 so it's these all appear to be operating as designed.

Okay, here's what we're gonna do. We're gonna power this thing down popping Z hood and let's take a look down below. Uh, my paper did say that about a year ago they had installed and replaced, uh, the spark plugs and uh, ignition wires. I Just want to pull one of those out real quick to verify uh, whether or not that's been done? It appears.

Yeah, this has been there for a little while. Yeah, I'm just gonna. we're gonna pull one out. Let's do let's do one that was misfiring so let's try for maybe cylinder I think Six was misfiring.

Yeah, let's go ahead and get some under hood light action going here. Surface of the Sun mode. Now we can see. so I rechecked the scanner.

It looks like cylinder five had like 36 000 misfires on it. So that's going to be uh one, two, three four Five is on that side or no, no, no, no I got that bass backwards. This is one, two three four. That right, there is Five.

Five is the easy one to get to. So let's pull that plug and wire out of there, take a gander at it and see if uh, maybe we just have a basic, uh, worn out spark plug issue. It's possible. Or maybe they never change them.

Also possible. Yeah, point being, we should trust and verify. Definitely trust and verify. So we're gonna go ahead and verify right now.

You know I probably could have verified before I put all this heat into this engine. but I'll be okay. Come here I need to get a hold of that little heat shield in there, give the thing a twist and then extract. Come on out you? okay and we'll hold the wire off at the coil as well.

There we go. All right. So I'm not noticing any like visual defects when it comes to that wire. It looked pretty good.

It's been replaced. it's not an original wire, so so far the gravity there we go. caught that one. So far the story with the spark plugs is checking out or the wires.
At least let's dig this plug out of here real quick on kicking. All right, take a peek at this plug. Okay, so here is our spark plug out of cylinder. Five Focus There we go.

that's looking pretty good. It's a Bosch plug. There's no excessive wear to it. The Gap is uh, it appears to be correct.

So I'm gonna give a a hard no on spark plugs and wires being the cause of those intermittent misfires. So let's get this thing back in its hole. and I think that since we had a bunch of misfires on number five, but not so much on number three, we can switch the coils I'm gonna try that now or next. I'm gonna switch coils out between Uh Plug three and Plug Five.

Then we're gonna restart the engine and we're gonna see if that misfire followed uh over to Uh cylinder number three and look at here. we can see there's a there's kind of a boatload of build up and rust on that coil. same one in that other one out back. Look at that.

I'm not saying that's the cause of anything, but it's probably not helping. So let's get that plug back in the hole, switch these guys out, and then see what happens next. All right. Reaching back down into this uh, hot, cavernous engine compartment.

here, we'll get this guy re-threaded, started, screwed down, plugged in. Actually, we'll plug it in last because I Want to switch a coil out Inspected faulty coils? You never know like they may be working I Mean they are working because it does fire, but it also may be. Uh, it may not have the voltage necessary to carry the spark with a full cylinder. meaning a cylinder that's been compressed and too much clickage, one that's been compressed light, and one that, uh, picked.

it has a fuel charge. And let's start with getting this, uh, engine cover off. here. It's just one eight mil bolt.

Pop that guy off and set that aside. Got our intake manifold? What is this as a wire nut? Oh no, No No, No no, no, we don't do wire nuts in automotive. No, No, no, we. That's no.

that's not okay. Not okay. But we'll do. We'll do that later.

What we need to do is dig out bulb number five. Swap it out with coil number three. should be fairly easy. We disconnect our uh, our plug wire here.

You get that guy off, and then two tens and then two connectors pop these guys loose right now. and then we can swap those coils in, swap them over from their position, and then we'll plug it back in and restart the engine and see if those misfires move over to cylinder number three. What? That's going to tell us? if it moves over, Then we have a a faulty coil, and since we have multiple misfires sort of scattered about and all this rust and whatnot on these coils, I would I'd be inclined to recommend eight coils, but let's not jump the gun. Let's prove it out first.
so let's see if I can just get in here with the impact, pull these bolts out hot. Come here. Bolt Coil Bolt Number two. Set those guys aside.

there's our coil unit. again. we've got eight of these, so we're gonna set that one right there. So I don't put it back in the same spot.

That would be embarrassing. Pull that guy out and we can just transfer it right on over. Ooh Hot Hot Bolts warm. So that's the number three coil in the number five spot.

click, double mix connector clicks going in with the ignition wire clicks. Next, reach down there hot, multiple small Burns There we go. I No longer have feelings and the two bolts. Let's get these guys in my fingers feel like those little crabs running through the desert where only one leg Touches at a time.

Get on there all right, Plug that guy back in, and then right here at our wire. plug that wire back in. Now let's head into the cabin, restart the engine, and see if those misfires have moved. I Hope they do, because that would be a real easy diet.

and if they don't move, then we know what it's not. Beginning engine restart sequence now. All right. Okay, we have misfire accounts pulled back up and number Five is just cruising away.

It increases again if I blurp the throttle with my foot. See that a couple little throttle blurps and five starts to really start to count. Look at that. 17 19.

Some misfires on Five. That's our. uh, that's our primary suspect here. Okay, that's a little.

that's annoying because so it's not. Here's where I'm at. We've got multiple misfires on multiple cylinders. Number Five is the worst offender.

So it's uh, it's not an air leak because my fuel trims would be kicking off a vacuum leak or a a lean code the field trips so it's not an air leak. If there were a vacuum leak in the intake, I believe all eight cylinders would be equally affected and appears to be biased towards just one or two cylinders for the most part. Again, number Five being the worst. Defender Um, I Don't think we've got uh, spark plug problem because it's got a new set of plugs.

It's not wires and it appears to not be a coil. Now, regardless of what those coils look like, if they're functioning, they're functioning. so it may not be that coil. Because that misfire didn't go anywhere, it's still on number five.

So that leaves us with possibly fuel or even base engine. Um, one thing before I start thinking about fuel or fuel injectors or anything like that. Let me go into. there's a menu called functional Test and there should be a feature called the crankshaft variation.

Learn Yep, there it is. And basically what this does is it re-measures the correlation between the camshaft and the crankshaft. Now I'd like to just go ahead and conduct this procedure real quick just to make sure that the ECM didn't forget that correlation or it's out of calibration for some reason. But what we're going to do, Follow the instructions put the parking brake on break indicated we're going to hold our brake, we're going to put it in park like so and we're then going to accelerate the engine to about 4 500 RPM in which the fuel system will go ahead and cut it off at that point.
Once that is complete, then the cam crate correlation relearn procedure is complete and then we just know that that's out of the way I Doubt, this is it. But I'm just crossing my eyes and dotting my T's so ready to learn coolants right. Accelerate to pull throttle until cut off occurs. Are you ready? Watch the tech.

Here we go full speed. We go test complete crankshaft variation. Learned. Successful.

Excellent. Yep, misfires are still there, but now we know. So here's what I'm gonna do. We're gonna go out and drive it.

I'm going to go ahead and clear these misfire accounts. That way they don't show up in history. We've already got all the data that I think we need. So I'm going to clear it that way on our test drive.

As it does misfire, it will log those misfires into the uh, the account feature and it'll give us a total number of misfires. that, uh, that we ran into that way I Don't have to do the math and subtract or add from 37 000 Whatever. I'm on a misfire, so let me go ahead and just clear this out right now and light is off. This is good.

Let's clear this stuff out of the way. I'm gonna go out and take this on a quick test. All right. Parking brakes off.

Let's get out of here. Troy Went and grabbed the gate for us so we don't have to. so uh, let's not keep them waiting Hawks For safety I mean I won't run you over Thank you sir. So what we're gonna do? We're gonna cut it right.

go over the bridge, give it some Full Throttle Action and hopefully those misfires show up. They appear to be only mid-range and they only appear to occur when the throttle is changing position. I don't know how relevant that is right now. it may turn out to be a factory.

It's been weird. we're back from the test drive now and now. I've got misfires all over the place on numbers Number three, there's 11 11 so far. counted on that trip on number three on 89.

Cycles Number one is showing 13 that have showed up and number five is down in the two range. so this is wildly inconclusive evidence. This is not helping me out whatsoever, and we're gonna need this next. I'm uh, I'm gonna go ahead and take a fuel pressure reading I Don't know if we have like uh, one system causing this or one component causing this or several components like the coils causing this.

So I all I've really got left is to uh, take as much information Nation as possible and then see if we can't come up with something here that's going to give us a direction to go in because I really don't want to just start throwing darts against the wall? Okay, you guys keep an eye on this gauge. I'm going to go ahead and key this on. We'll take a measurement while it's keyed on, then I'll start the engine and it will take an engine running measurement as well. We got there 60 pounds.
Yeah, that's fine, not the problem. Well, we're spending a lot of time finding out when it's not something weird is going on here. I Uh, nothing's really making sense on what's causing this because I'm getting these random misfires all over the place and I kind of kind of shouldn't be. I have learned that when you start to get stumped, time to check your grounds and I've seen a fair bit of rust on this particular truck.

so I'm I'm wondering how our ground connections are. Let's uh I think there's like two or three primary ground connections that service most of the powertrain control. Let's go through and find those Ground locations and then see what kind of condition they're in. If they're all crusty and rusted up, we can go ahead and maybe clean those up some and then recheck.

and uh, if not, it's just another dead end. but then at least we'll know what. It's not all right. So I've gone into the all data and we're looking at the wiring diagram that shows all the the primary grounds.

Now we've got all of our ignition coils here. One Bank Ties into a harness ground Second Bank ties into a harness ground and then we scroll on down to G102. so there's a ground connection on the left side of the engine block. We have to keep that one in mind.

All right. So I can't really see where that ground is supposed to be. Uh, from up here on this side of the engine. I Believe it's going to be the primary connection at this ground cable where that meets the block.

let's see. can't see it through the uh. the wheel? Well here. Oh yeah, yeah.

look back there. right. way back in that hole. that's the lug for the uh.

the ground cable. See if it's going to focus here? Yep, now look at that right there. There's another ground wire right next to it. See that little guy sticking out on the left.

That 80 bitty little guy. that's the ground wire that ties all the grounds in to the coils. Uh, that's a pretty nasty looking ground wire right there if you ask me. Um, I'm not saying that's the problem, but it could be a problem.

now. there are two more Crown wires of consequence and I believe they involve the ECM and those are usually yeah, right here on the inside of the freight or outside of the frame rail just under the driver's seat. you've got a couple more crusty looking grounds right there. Uh, I'm gonna go ahead and pull those guys off and clean them up.

Those are easy access and we'll reattach those guys and see if we get any change of state. And if we have to, we're going to go into that wheel well and clean up that that body ground or that engine ground and or create a new engine ground. I'll probably just make a new one. Yeah, I Actually fear, uh, kind of breaking that bolt off in the block over there.
So perhaps uh, I'll probably just run a new one and then not have to, uh to worry about causing any damage because I Do see, there's some. It's like some Northern rust going on with this thing here. Anyway, let's pull these two ground wires out, clean them up, and uh, we'll get these guys back in position for a retest here. Let's get thank you.

Wrong size socket. Is it now a 12? Yeah, it used to be a 12. it's all rusted. Would you believe it? I Finally come over here with the right size socket and due to heavy corrosion it's not going to fit or it's at least gonna slip.

So let's see if I can't get a 12 on there. That's a negative. All right, let's try something else. So we've got a wrench 13 not doing it because the 12 doesn't exactly fit.

Uh, let's see. Make it fit. Hammers our hammers all right. It's broken loose at least now we can work on it.

some loose turn or not. Ah, that one's that's not gonna do it loud un click allowance that's crusted up pretty bad too. Come on now, the bolt is Rusted to the ground cable. see that it's taking the ground with it.

Okay, about a half inch out. who fits all right half inch bit. So it's now standard sized. And this is not fun for me because I don't even know if this is the problem.

So I'm putting a lot of effort into a non-issue take a look at this one here. not that bad. It's kind of chowdered up, but we're gonna clean it up anyway. I'm gonna go in there with the Ziz wheel.

polish off some of that corrosion. Shiny, shiny ish. Okay, this is better than it was. Let's put that guy back on.

I Think that would be the one in question. It's either this one or this one for the O2s I Don't really know, but they both need cleaned up. Maximum clickage? There we go. That one on the other hand I don't know if that's going to come out of there I might end up breaking this wire and those are both chowdered up pretty bad.

I Don't like that at all. I'll tell you if that's not a problem now it will be. break that wire or something just to get the thing to come off. Break loose.

Send it. Yeah! I don't like this. See how the wire is looking? I might have to just put a new, uh, new terminal on the end of this wire. I Think that's what I need to do that one.

That one stayed put. didn't it that little one up top? Let me see. yeah, that one's good here. Maybe I can jar the rust loose and it'll let go.

Probably not. Looks like I'm changing this whole eyelet here. Yeah, that's not gonna. It's not gonna work.

Okay. You cut that guy off and uh, we'll get that bolt out of there. All right. Crusty wire.

You're coming with me. How many is that? that one wire or a couple wires looks like it's two. There's two of them in there. Oh, cut those out right now.
Goodbye. Hmm. So let's see. let's go ahead and pull this tape back.

and I brought an eyelet with me. So what I need to do is just, uh, get these guys stripped real quick. Like right about there. Let's drop that back.

Come here. Yeah, that wire itself looks good, so there's no corrosion traveling up under the insulation. That was a moderate concern. Now take my new replacement pilot.

Run these guys in the hole there. Oh no no, no wait. I'm I'm ahead of myself. My heat shrink forgot my heat shrink.

Is it gonna fit over? Yeah. All right, we're fine. Never mind. come in.

crimp this guy down. Nice, good, solid crimp action here. Double crimp right there. That's good.

and I'll just throw some heat shrink over that for, uh, for good measure. It's a little wet. I'm kind of like laying in the water right now. Sort of a little torch action Here we go.

Let's shrink our heat shrink. Get back up there. you. We'll drink it with the water on it at all.

I Don't care. All right, we are shrinked and shrunk. I'm gonna go ahead and clip off that extra wire that's sticking out. We don't need that, it's just gonna get in the way.

Clip that off. it's uh, it is useless. Let me hear you. There you go.

Get rid of that. I'll tuck this back inside of the convolute. it's a little warm. put that back in there so it stays looking pretty.

There we go. and I'll go ahead and put our bolt back in and run these guys down. I'm going to sandwich the new repair behind this older bolt or the old lug like. so that way the new one gets grounded first and because the loop on the new, uh, new little lug there is larger in the existing.

Loop Did I Clean? No. I didn't hang on I did not clean frame surface off right there. Let me get that real fast. Hang on there now.

I got it. Good good, good lid on my side down here and it's starting to hurt my neck sideways. Mechanic: all right. click action, achieve cool beans.

Let's get out of here. fire this thing up and maybe cross our fingers. Perhaps we'll uh, we'll have some resolution I don't think so, but you never know. Okay, back into the cabin, restarting the engine.

Okay. taking a look at current misfires, we still have a few counts starting to show up. so that's a that's a big negative. We do not have a successful repair on a on a faulty ground.

Yeah, there's a bunch that showed up down there on number Six. Number Five's got one. Yeah, so we're a little off base here. It appears that cylinder six now is the one that, uh, that's biasing towards the consistently misfiring cylinder.

Let's scroll down to the history. Yeah, not much history there, but number Six seems to be favoring. But uh, it's not number five and it's not number three which kind of blows my coil Theory out of the water shutting down again. I Recall when I was trying to excite the misfire condition and get the scan tool to pick up on it I had been kind of blurping the throttle uh I had foot on the brake, a little bit of load on the engine and I was just kind of going through a preliminary sweep like you know not Full Throttle or not half throttle.
not like highway or cruising, but just little bit right off idle and I noticed that as I gave it throttle the moment I came off the pedal and it was returning to idle. that is when uh, when those misfires were occurring. So I was thinking maybe I'll take a look at the throttle position sensor TPS percentage and if I go through with my foot and I follow TPS as we move slowly the desired throttle position sensor that's highlighted and then the actual measured. They are in sync and they correlate with each other right? Did you notice that right there when I let off see that sudden change in value seems to be a little slow and if I feather the throttle I get discrepancies in the numbers, see that it's like there's a delay and I noticed that that is where the misfire came in was during that observed delay period I don't know if that's actually just normal and the the throttle at the engine is responding slower than the pedal input and I'm just overthinking it out of frustration.

but I am noticing that that slight alteration when I quickly move the throttle. There we go 60 and 47. You see that? So let's go and just take a look at the throttle. Perhaps the uh.

the throttle? Plate's hanging up and it's all clogged with carbon and whatnot. Couldn't hurt because I don't know what it is, but we can at least find out what it's not. Uh, the acts of desperation start cleaning. Oh gravity.

Go come back. start cleaning things. That's uh, that's all I can do I guess because I really? uh, I just don't know. Okay, let's see what we've got there.

So here's our throttle body with one single throttle valve inside. It's electronically actuated, so there's a motor in there. That motor takes the uh, its signal from the PCM the PCM takes six signal from the accelerator pedal. uh down inside of Dash So here's how I'm gonna make this easy.

We're gonna grab ourselves a uh throttle pedal depressor I'm going to key it on. We're going to depress the pedal. when I do that, it's going to open up the throttle body and then I can go in there with some cleaner and spray that out because I I Know that carbon buildup looking the varnish stuff right there is probably not the best and uh, it doesn't actually have to be there. So let's clean that out.

and then, uh, well, we'll start it and recheck it again. So what I need to do? Key that on. We'll put our pedal depressor on the pedal and we'll hook it to the steering wheel here. It's like a caulking gun.

We'll run the thing down I vent too far. We'll run it down, depress this to 100 throttle, and then we can go in through the throttle bore there and clean that business out. It's not terrible, but it certainly is not helping the situation and since we don't know what it is I Got to try to figure out what. it's not okay.
So with the throttle plate held open, we'll go in here. I've got some some BG throttle plate throttle body cleaner Supposed to not be, uh, horribly solvent-like as if brake cleans. Similar to brake cleaning because some of these throttle bodies have like a protective coating on them and it's designed to not wear away the coating anyway. I Threw some cleaner in there.

It's going to go in with this towel and wrap around the fingertip here and just kind of Polish away all that build up. I Feel a bunch of it right here. There's a bunch on the top spray. Go wipe that down.

We'll get the throttle bore and then I will go through and wipe the edges of the actual plate. There we go. That should be sufficient. All right.

So let's back it up. We'll plug our intake tube back in real quick here. Go back into the cabin, restart the engine not at wide open throttle. It's going to stumble at first and misfire a lot because there's a bunch of that cleaner inside of the intake.

But once that clears up, we can go back and recheck for the misfires again. disconnecting. Full Throttle Now there we go. restocking the engine.

Come on. Wake up. Come on there we go. Good.

Okay, just as before, put on the brake and then we'll put it in drive and I'll give it just some light throttle. Taps right there in that sweet spot And that's where we found and fell and monitored the misfire. You guys see that there's a whole bunch of them starting to add up that had almost no effect at all. Yep, there's our history.

They are occurring right now. Yep, there's two, Four of them. Five? Yeah, that did not seem to help at all. Okay, no change.

Back to the drawing board. Powering down all right. So out of frustration, I've got engine data pulled back up and I'm I'm kind of looking for anything that I don't think is right and I'm looking for something that can affect all the cylinders. Um, without something being specific.

For example, earlier, we tried to troubleshoot that cylinder. five. It seemed to have been misfiring most frequently. We moved the coil, moved the wire, check the plug.

That was a solid No, that's a negative. We checked grounds where there was known problems down below. I Substituted a ground in at the one on the side of the block because I didn't want to touch that one. so I went in there and clipped to it with like a real long extended wire clip and then I ran a a known good ground and I also piggybacked a known good ground to the terminal up here at the ignition coils.

so that eliminated the grounding issue. It's not that it's not the sensor, it's not or the uh, the ground's down below. It's not the O2 sensors. those are both brand new.
They've been replaced previously, not by Yours Truly but by another. So it's not those the sensors appear to be operating as normal I don't think it's a fuel issue, so what could it be? I cannot figure it out in my head I have only but one choice and that is kind of to return back to basics and I'm gonna put this thing into the condition. you know again, light throttle burps with the pedal. I'm going to put it in into a condition where uh, we we saw the malfunction taking place and I'm gonna go through and we're gonna record all of the the data that we've got.

So let's start with the O2 sensors. Bank one up and down. That one's behaving Bank Two, that one's behaving scrolling down everything else that can affect this. Our fuel trims are what they're supposed to be.

See that field trims are exactly where they're said to be. So what else is left? We have temp sensors because the ECM uses temp sensors to determine its overall fuel mapping. Our temp sensors appear to be accurate intake temp sense that sensor that appears to be accurate. the mass airflow grams per second.

We haven't talked about the mass airflow. giving this thing some throttle. The mass airflow appears to be responding. Airflow is going up as I give it more throttle.

Airflow drops when I take away throttle. We get a big rush when I blurp the throttle but looking at its frequency I think that's a little high 3000 Hertz 3 100 Hertz I think we saw 43 I Mean that's that. seems a little high I Don't think there's like a spec on it, but uh, like a specification, but that did seem a little high. Uh, our ignition Advance is good.

We know cam crank correlation is good because we did the relearn on it. We checked out our throttle position sensors. The manifold pressure sensor that's good voltage is accurate I'm I'm running out of what it is I I Hate P300 codes. You know what? it's time to do something or get off the pot.

We're gonna do something here. All right. I'm done overthinking this. so we've narrowed it down to either a fueling issue.

Doubt it. We've got good fuel pressure. Could be an ECM issue. Doubt it.

So the only other things that we have that are in common that tell the ECM how much fuel to give it is its sensors that tell it how much air is coming in. So according to the scan tool, the mass airflow sensor is mass air flowing just fine. Parts Cannon I'm ordering another one. That's right, it's time to get off the pot.

I I Think something is going wrong with uh, this mass airflow? or I think it's extremely possible, if not likely considering we've already utilized the process of elimination and we know it's nothing else. I Really doubt it's base engine? Uh. I've seen these things come in that are way more destroyed than this and they ran much better than this. So it's got to be a some kind of a sensing issue at.
perhaps this mass airflow is biased and the ECM is not detecting it. You know, maybe it's dropping out, the signals getting lost intermittently. or maybe it's really slow responding. similar to a like an O2 sensor that failed.

How sometimes they can get lazy and they don't operate. See what that looks like in there? That's there's. the sensing elements way down inside of there. I Think there's three of them inside of this.

uh, particular unit? See that little guy right there in the middle between those vertical bars? There's one of them. There's the second one, and the third unit. third sensing elements right up there. now.

Those appear to be in pretty good shape. They're not clumped up with dirt or anything. so I don't think we have a dirty sensor issue, but uh, perhaps something's going on with the serpentry inside of this unit. I'm gonna order another one.

We're gonna toss the guy in that's the ambient air temp sense probe right there. You see that little ball thing sticking out, that's the temperature anyway. I Digress: I'm gonna order another one. We're gonna toss a parts Cannon replacement part into this and then we're gonna pull our data back up and see what happens.

Something's got to change I need to initiate some kind of a change in this engine. Okey-dokes I Return. We've got our old unit right here. It is a Delphi See right there that's a Delphi OEM unit and I ordered another Delphi There there was a more cheaper version available and I chose to not buy the Cheapo one because I need to make sure that this thing works exactly as it's designed to work again.

We've got the three sensing elements one two, and the third one down there. There's our temperature probe right there and we have an indicator on the front of this unit that tells us the direction of airflow. So let's get our intake boot back on. Get this thing slipped onto the air box lid? There we go.

Plug you in! I Know this is what's wrong with it I Know it is. You know why? Because it's nothing else. It can't be because I know it's not throttle actuators. it's not the ECM It's not a vacuum leak.

It's not that P0455 code. In case you're wondering, that code does not cause misfires to occur. and if it did or if it does and that's what it is, that's that'll be a first for me. So I could be very wrong What? We're going to do this instead first.

I've spent a about two hours at this point poking and prodding at this thing, getting frustrated out of its misery. and Uh something's got to give here. so it's gonna be me. I have folded I've ordered parts of the Canon gun gravity show.

Let's head back into the cabin, fire this thing back up and let's take a look at our data once more. climbing in, climbing in and restarting the engine again. All right engine running. Pull data up with a quickness.
I Want to see if things start to change O2 sensors those are working. They still appear to be switching. Let's see, let's find fuel trims. That's a new one.

Look at there. We've got a positive number on the short-term fuel trim and a positive number on long terms. Let's put this back into the conditions in which the misfires were present. Oh, look at that.

Let's give it some throttle so we're positive in the fuel trims all of a sudden, so something's changing, especially if it were short terms. I'd Pay it no mind, but check out our long terms especially Bank two Yeah, something's happening here. You know what? Let's go. Uh, take this thing back on the road real quick.

go for another Spin and we'll see if it's uh, if it's giving us misfires while driving. but we're not going anywhere with the uh, the hood open all right. we're outside the gate. Click it or ticket for safety.

Let's get out of here all right. traffic's clearish here we go whole Steam All right. So we just started going, but so far so good. I think it feels okay I'm not going to get my hopes up because this has been a total dead-end job uh since the get-go but you never know we might have got it.

Let's give it some power, pull it up onto the bridge here. we're going wide open and then as we Crest the top of the bridge I'll come off wide open throttle, we'll let off and Coast all the way down and then we'll pull back with the way we came and do some stop and go City driving and uh, which point I'll uh I'll pull over, we can pull up the scan tool data again and we can check out our misfires and misfire histories. All right. So that deceleration back there felt pretty good and I say that with Rising inflection because I'm trying to keep Supreme confidence inside of the situation I don't I don't want to speak and and then be wrong and then have to eat my words I hate that everyone is that two ears in one mouth.

That means you should listen twice as much as you speak so on occasion I refrain from speaking I Don't want to wait for this bus. so we're going to go this way. I Think we came. isn't it? No, no, it's the neighborhood.

Yeah, let's get out of this neighborhood and find a parking lot. I'm not gonna sit on the side of the road around here and make people question what I'm up to. That would not be okay. Suspicious Vehicles Parked in unknown neighborhoods with suspicious occupants.

It's negative attention. We don't want that. This guy's just riding. Look at him.

All right. it's not even a Friday night. I Need to come back to this neighborhood on the weekend. This place is full of activities.

Ah, here we go. Vacant church parking lot. Now we're safe. Let's go over here and hang out and check out our data.

I Like to park in the middle of the parking lot that way you can see what are approaching. All right parking. ziato. Let's go ahead and pull up.
I'm not gonna look at misfire data just yet. Let's look at sensor data first. I Want to see if those fuel trims are still climbing or if they've stabilized at this point? We will know by what the short terms are up to. There we go.

Got a long term? Uh on Uh, Bank two? that's seven and eight In the short terms are zero and zero. So our short-term fuel trims are uh, they're level so it's not trying to adjust. Uh, in the moment, let's give it some throttle and see if short terms do anything. you know everything's still reacting.

We're going negative as we add fuel, it pops positive a little bit at idle. That's good in our long terms are favored and hanging out at six. and they're not climbing or going through the roof. That's actually good because we have a noticeable observable change in engine data.

Okay, so we're still in. Drive Let me give it some more throttle blurps and then we're gonna keep an eye on our current misfires. which are what do you know? Look at that. Zeros and our histories throughout this entire drive cycle are also hanging out in the zeros.

Sweet. Okay, I think we're kind of getting somewhere. it's better than uh, than what it was for sure. and we don't.

Uh, well. I don't feel it I Felt it earlier. We had measurable misfires earlier all across the board and as of this point, right now, we do not. So I Guess what I think has gone on here is that mass airflow sensor was not exactly accurate.

It was working and it was measuring air and it was measuring and calculating the air flow into the engine. But I don't think it was doing it quite accurately and we can assume that based on our mass airflow reading at idle, we had a high nine grams per second reading uh, earlier and then with that new sensor, we ended up with an eight. The frequency didn't change, but the fuel trims started going and at changing, especially on the long terms. And so simply based on the long term I believe that it was, uh, running at an incorrect air fuel ratio and because of that, we were getting those, uh, those light misfires between load and unloaded, or coming on and off the throttle.

and as it appears that the scan tool is backing up that uh, that hypothesis. Anyway, let's head back to the shop. Uh, we'll let this thing run for a little while. I've got a couple of things to look at and I want to recheck all of our misfire accounts when we return? All right, a few miles later, we're back at the shop.

Park The auto. We're still in the history uh, history list here. Let's scroll it back up and see the currents one more time. I Think I think we got it.

Look at that. a bunch of zeros I give it some throttle blips, it doesn't care. Phone to Bar All right guys. Well, that one kind of threw me for a loop.

Uh I I think we got it. It's pretty much dialed in. I'm gonna let this thing cool off and I'm gonna give it. one more test drive, but not today.
it's it's actually super late. I'm here. it's almost seven o'clock Uh, but this thing was. uh, it was frustrating me and I wasn't about to go home with without an answer because without some kind of progress, that's the kind of thing I lose sleep over.

So I've got a I've got some good direction on it. We have an improvement. Fuel trims came back into line and I'm feeling really good about that. As I mentioned earlier, there is going to be some other actual work on this and I'm really sorry we ended up being stuck inside of the scan tool on this entire video.

I Expected to find uh, you know, vacuum leaks or something like that. but uh, you know you never know what you're gonna get. So that being said, I'm gonna go ahead right about now and close this video out. I'll do that as always by thanking each and every one of you guys for watching this video.

Hope you enjoyed this video. If you did enjoy this video, let me know about that by tapping the like button down below. Don't forget to drop me a comment or two while you're down there. and most importantly, every step's a great day.

See you guys later in a video in a transmission. No. I didn't forget I'm terrible finalized powering down.

100 thoughts on “Dreaded p0300! we know what it’s not! 2005 6.0 5.3 lq4 p0455”
  1. Avataaar/Circle Created with python_avatars Chris Hill says:

    He acts like he's a Robot.

  2. Avataaar/Circle Created with python_avatars Chris Hill says:

    Your a really talkative guy, your very good at what you do but you don't have to explain what your doing every second of your video, people see and understand and see a lot what your doing, everything don't need an explanation.

  3. Avataaar/Circle Created with python_avatars Dustin Shadle says:

    Ah I really do love my old carburetor

  4. Avataaar/Circle Created with python_avatars T Casterson says:

    put delco plugs in. i wouldn't use bosch in that engine.

  5. Avataaar/Circle Created with python_avatars Dave Kube says:

    Thanks for all the info on how to utilize my 'spensive scanner better! Loved this!

  6. Avataaar/Circle Created with python_avatars Hola! DakLak Digital says:


  7. Avataaar/Circle Created with python_avatars Dave P says:

    Back to basics, man. Combustion engines need air, fuel, spark and compression to function properly. You eliminated fuel and spark…. The whole reason I got out of automotive repair is all the electronics. Too many computerized variables.

  8. Avataaar/Circle Created with python_avatars James Adam says:

    I have noticed that being the owner of an '03 Silverados and Avalanches were phenomenal for lifter drops and cam spalling.

  9. Avataaar/Circle Created with python_avatars Doug Pollard says:

    I really enjoy watching your videos.

  10. Avataaar/Circle Created with python_avatars sun enfun says:

    MAF update

  11. Avataaar/Circle Created with python_avatars Dale Babbitt says:

    Without being in the scan tool we would not learn if the changes made along the way made a difference or not. Diagnosis is necessary.

  12. Avataaar/Circle Created with python_avatars Jacob Godfrey says:

    Should have recheck the hertz to see if that had changed also

  13. Avataaar/Circle Created with python_avatars Justafatredneck says:

    I seen you cross thread that bottom bolt on the #3 coil with the impact… 🤣

  14. Avataaar/Circle Created with python_avatars Frank Cara says:

    I noticed when you took off the MAF there where 1 or 3 which looked
    Ike bugs in the screen which my give a partial short which could of been the problem qlso

  15. Avataaar/Circle Created with python_avatars Todd Bevins says:

    On the issue of the airplane performance – Airlines have regulation requirements to calculate landing and take off distance. When the temperatures exceed what the charts go up to they are not allowed to "wing it" and just extrapolate what the landing or take off distance will be. Its not that the planes cannot perform well enough in these temperatures it just comes down to what the operating manual must the chart that covers the range. This happened back in the 90s in Phoenix AZ too.

  16. Avataaar/Circle Created with python_avatars David Ray says:

    Ray I enjoy watching your videos! I'm currently having the dreaded p0300 and this video gave me somethings to look at and to know what it's not. I'm thinking that one of the sensors is having an issue because it stalls and will crank but not start sometimes.

  17. Avataaar/Circle Created with python_avatars Tripod says:

    Hi Ray, got a question for you, did you know what Canada are trying to do to Mechanics, from 2024 the Canadian Govermnent are Banning Brakeclean, WD40 and ether, basically products like these they're banning from use, personally I think it's ridiculous, just wondered what your thoughts on this, and is it possible that Biden might do the same thing as Trudeau. Take care with the weather.

  18. Avataaar/Circle Created with python_avatars Cullen Pulis says:

    I've seen wildly inconclusive data whenever there is multiple misfires, I think when manufacturers use crankshaft speed to detect knock when multiple misfires occur, the computer gets confused as to which exact cylinders are missing and just stacks most of the counts on cylinder that it first detected missing. That's wht it seems inconclusive after you clear codes and detects a different cylinder first

  19. Avataaar/Circle Created with python_avatars Clinton Turner says:

    This was a good video.

  20. Avataaar/Circle Created with python_avatars Roger Wilson says:

    Good to see beautiful wife unit..a little pretty in your video

  21. Avataaar/Circle Created with python_avatars John says:

    Too much camera flailing, makes me nauseous so hard to unsubscribe. 😳

  22. Avataaar/Circle Created with python_avatars Bakhtiar Dusky says:

    At the end just for test You could have used a picoscope on maf sensor and compare both wave form to see what is wrong with it like maybe the voltage is dropping or something like that caused missfires.

  23. Avataaar/Circle Created with python_avatars Yaakov יעקב המיקסברג says:

    So…what about the Clunkage in the Drive Train like rear Diff or shaft on Silverado.But great solve doc.

  24. Avataaar/Circle Created with python_avatars Suzuki Kawasaki says:

    The system is smart enough to say misfire but not tell you what's wrong. ODB my ass… 😂

  25. Avataaar/Circle Created with python_avatars Romley Hardy says:

    Your videos are great!

  26. Avataaar/Circle Created with python_avatars derk anderson says:

    Its not global warm the earth is just now coming out off the final bits if ice age just think back to dino time there wasn't to much ice then ether love videos keep at them

  27. Avataaar/Circle Created with python_avatars Silent Krickit says:

    Im thinking don't piss the wife unit off or she can make u a little flatter

  28. Avataaar/Circle Created with python_avatars Michael Casteel says:

    Hey just an fyi i have had alot of problems with bisch spark plugs lately

  29. Avataaar/Circle Created with python_avatars Jim Gandee says:

    Great job sticking with it!

  30. Avataaar/Circle Created with python_avatars Lionel Cantu says:

    Your videos are full of useless time. I'd like to see you just get to the point and highlight all the problems

  31. Avataaar/Circle Created with python_avatars Howard Neumann says:

    Crankshaft sensor

  32. Avataaar/Circle Created with python_avatars Katie Luv says:

    Pretty sure that was the look of an employee that would rathe be flipping burgers that cleaning that wall.

  33. Avataaar/Circle Created with python_avatars Leif Nilsen says:

    👏👏👏👏👏👏👏 wat to go. Your do diligence and skills is impressive

  34. Avataaar/Circle Created with python_avatars Alvin Hyman says:

    I feel you on this one. I chased a p300 on an 03 F150 turned out after much process of elimination and turned out to be a faulty mass airflow sensor. Chevy and Ford share some similarities!

  35. Avataaar/Circle Created with python_avatars LowMan Josh says:

    Gm 5.3/5.7/6.0 and even the older vortec 4.3 all have common issues with the lower intake gasket failing and causing a missfire I know my 02 blazer xtreme had this issue and my my step dad's 98 1500 with the 5.7 also had the same issue. Also seeing a wire nut :/ someone's been in here and didn't fix it right

  36. Avataaar/Circle Created with python_avatars Daddyoh says:

    How about injector balance or check your Vaccum It should be around 20hg steady. if bouncing maybe valve springs. partially clogged cat.

  37. Avataaar/Circle Created with python_avatars Daddyoh says:

    We need to go back to the R12 AC refrigerant.

  38. Avataaar/Circle Created with python_avatars MJB says:

    Cleaning out the throttle body like that rarely if ever makes a visibly noticeable difference. No more than the stuff you pour in your gas tank. Gas line antifreeze is nothing but rubbing alcohol. Same with winter windshield washer fluid.
    The reason we have two ears is that the ones we get are crap. You are lucky to make it to retirement with any hearing. Some of us don't make it to the age of 6 mos with all our hearing.

  39. Avataaar/Circle Created with python_avatars J Brd (Jbrd) says:

    well done ray

  40. Avataaar/Circle Created with python_avatars Jack Dapirate says:

    comment xfgdfgfsghfsgh

  41. Avataaar/Circle Created with python_avatars Alan Armstrong says:

    Differential noise.! Something is slack or broken in there.!

  42. Avataaar/Circle Created with python_avatars Larry Schmidt says:

    just curious you spent about 2 hrs worked overtime cleaned some grounds and cleaned the coking out of the throttle body plus whatever else , I'm wondering what was the bill?

  43. Avataaar/Circle Created with python_avatars Larry Schmidt says:

    I've seen a MAF with one timy piece of contamination on it like a piece of a bug or something cleaned it and fixed vehicle