In this video I have a look at a customers Chevy Trailblazer EXT with the big 5.3 that has a customer complaint that the vehicle will not run a drive cycle. I give you a small list of items that will inhibit the drive cycle and we find the issue right off the get go. However a Napa part throws us a red herring.
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Oh, it wouldn't be an SMA day without a Chevrolet We got a Trailblazer here that supposedly won't run the monitors, so this can be a tricky one. Um, for a lot of reasons. There's there's several items that'll stop the monitors from running and sometimes people are trying too hard. Also, got some keys here.

What do I mean by that is people who are semi-mechanically inclined. We'll be inclined to get a drive cycle process sheet. You know via the interweb all I Got to scan till it's completely dead so this is useless. I'll be right back.

Okay, we'll try this one. this one's not as dead. Um I think I was saying that you know people will get the drive cycle process sheet. You know the exact parameters and driving rules that a car would go through to run the drive cycle and then they try so hard to match that that they just never drive the car normal.

So whoa. Um, so I've seen that before and then of course I made this a little list here. The guy left me a list of some parts that had been changed in the process up until this point. Things I Think of when a customer says the car won't run a drive cycle or is fouled on the official sticky note: Intake air temp, coolant temp brake pedal input Prindle input So park reverse neutral drive low AC input fuel level input, vehicle speed sensor, barometric pressure, a throttle input and then last but not least the cam the keep a live memory is that resetting every time you turn the key off.

So these this is a very short list of of items that will make it and hit a drive cycle. you know, just look around these other things like four wheel drive input. you know, electrical load. There's a lot of things typically on.

GM it's coolant temp that's what. I find the majority of the time on these and it doesn't always set a code. you don't always get a po128. I'm gonna let this Auto ID I just did one the other day on a 2001.

Buick Century older old junker I would not run drive cycle. guy drove it for like 800 miles. no drive cycle. He never mentioned though that when you're driving the temperature gauge is up, down, up, down, up, buried in the hot back in the medium you know.

and it was just a bad coolant temp sensor. Simple as that, so that was easy. So I'm going to get some data here that I think is going to be relevant to us. we're going to look at it and then we're going to take her for a rep.

and my advice would be is when you're looking at drive cycle parameters always start in generic. OBD2 So yes, we have two monitors that are incomplete probably Catalyst and Evap is going to be my guess. Catalyst and Evap the other monitors are complete. We'll see if we have any pending codes, no pending codes.

So I'm going to go and poke through live data and get stuff that I think is relevant to us. So first thing I Noticed right off hand: uh, intake errors: 39. It's probably 37 or 39 degrees outside. That seems right.

Barometric pressure seems pretty close. and then engine coolant temp though is sitting right here at 59 degrees. I'm pretty sure this guy dropped it off last night, so it's been sitting for a long time. Let's go out under the hood, let's find that coolant sensor and let's see what the actual engine temperature is with the infrared thermometer.
Well lucky lucky so that coolant sensor has been replaced along with the pigtail. Of course we don't know if it's made from the finance of Chinesium. Everything Feels cold? Let's just see ambient wise outside here. Where to shoot the hood blanket? We're 35 degrees F Shooting the engine, it's 35 degrees.

We shoot in, down and around the cylinder head. it's 35. Everything's 35. This thing is.

Stone Cold Radiator upper hose is 36. 34 33. So I think it's a fair assessment to say that this is where we have to start because that is definitely skewed. So before we do anything, I'm going to get a coolant sensor I'm not going to pull the vehicle in I'm going to get one that we know is good hopefully and see if our results are still mixed up.

Snap has one of those Court sensors. We're going to bring it up. We're not even going to stick it in the cylinder head, We're just going to plug it in and see if it's reading ambient temperature now. I Gotta be careful handling them because it'll you know change just from the heat of your fingers.

It won't take a tough so that's going to tell us right away. Is there a problem in the wiring? You know from there the PCM is. there's some resistance that's you know, creating this you know erroneous temperature reading or is it just a crappy sensor. My experience with GM is usually the coolant temp sensor and it's always skewed just a little bit or it's erratic, has a dead spot in it as it's warming up.

So and why is that important? Well, if you look in service data, uh, the writing criteria to start a drive cycle for some of the monitors requires what GM would consider a cold start where a lot of Manufacturers consider a cold start. So uh, it's barometric pressure within a certain you know PSI range or kill Pascals how you're going to read it. Engine coolant temp between 40 and 86 degrees Fahrenheit for this, uh, vehicle intake between 40 and 86 degrees. But here's the kicker is the difference between the intake air temp and the coolant temp has to be within 14 degrees.

So therefore you know this one skewed more than 14 degrees even though that coolant temp sensor May read good on its you know, high side on the high end of the scale. If it never hits that criteria when it cools down, uh, you don't have that 14 degree differential between intake air and coolant temp. It's never going to run parts of the drive cycle that require a cold to start, which must be evap. and Catalyst because that's usually what I see.

That's what I just saw in that last Buick I did. and I've seen a host of things like see everything from you know, brake input to being bad. you know, coolant temps a big one, thermostats that just never quite hit the operating temp but do not set a p0128 I Mean there's all kinds of stuff. alternators that overcharge.
Um, you know, just every case is a little bit different I got lucky on this one. just saying. You know, coolant. let's look at that.

It may not be the case, but this is where we're starting. All right. Well, Nath it showed up like I say well, it's been I don't know. It's probably been 45 minutes since we last spoke.

It's a classic TS Five Seven Three Two feels warm, but it shouldn't take long to adjust. We will unplug this one again. We're just gonna leave the wires hanging right here. Plug that in.

sit there for a moment and we'll see what it says on the scan tool. All right data. I'm gonna let that sit for a little bit because I can say it was in my hand. It was sitting inside in the Box warm on the Shelf so we'll give her a few minutes.

It's been a while. 57.2 is where it's at, so let's just go out here for put my laughter okay, just dangling. Yeah, no, we're still 34 degrees. so I think it's plenty cool.

Uh, how about this? Let me set you down. I Don't have my tripod, but theoretically when we open the circuit, if there's no resistance in it, it should go to minus 40. right on the scan tool. That should be as low as it goes.

Let's go have a look and see what this just did. Yeah, we're not quite there, right? We're at minus 38, so there must be some added resistance in the circuit somewheres all right, So it's kind of interesting. Well, at least we're armed with a little bit of knowledge whether it's the right path of the wrong path. We don't know yet, but we're gonna bring it in before it warms up too much here before we run out of parking spots here.

Man, tow trucks are dropping off faster and we can fix them. Okay, let's um, let's think about this: I don't want to mislead you guys. So our reading is skewed obviously. So we're sitting here at 75 degrees.

Um, I got us a thermocouple here. Let's just see. so they're sitting here in the shop that says it's 63 degrees. Okay, let me just see what it is on the tip of that coolant sensor.

So we have a kind of a baseline. That's what we're looking at here. It should be about same it's been sitting here for a little while. It says 62.8 63 62.4 So it's kind of bouncing around here, but somewhere between 62 and 63 degrees.

and we look on scan data and it says 75 degrees I Don't know if I can get this so you guys can see it better. But yeah, 70 75 degrees. So it's like 10 degrees off. Uh, and it's 20 degrees off from what it says ambient temperature is.

So we have to think how this coolant sensor works. It receives a five volt signal and then it has a ground and it's essentially a you know, a resistor that changes. Um, as temperature increases. So as temperature goes up, the resistance value goes down.
it becomes more of a short so to speak. Until it's you know, you know Zero Ohms is you know, 200 and whatever degrees 284. Um, open circuit high resistance. So the highest resistance you can have is open circuited and that's on.

I Think minus 40 or so on these vehicles. Um, so that's how that sensor works. So what are we seeing? We're seeing an increase in temperature so that means our resistance must be going down. And that circuit.

our resistance is, you know, shorting together so to speak. A few ohms of added resistance. So what does it do when we open circuit it? unplug it. It goes to minus 38.2 Okay, what's it do when we short? It should have a pair of players.

It goes to 284.. So from 284 to minus 38. that's its range. Um, what is the open circuit of the intake air temp? When you don't plug it, we get a plug here.

get the lock on it. So intake air temp unplugged. Minus 38.2 So that must be open circuit. They both match.

I Thought it was minus 40. to be honest with you, so that's kind of bizarre. I Thought these were minus 40. Okay, well, whatever.

Uh, something to think about. Um, and this is reading about 10 degrees C Let me grab a voltmeter for us folks. All right, let's just see what our open circuit voltage is here. Okay, we're gonna put this battery negative.

Looks like our battery is dying because on the scan till it's 11.6 but that that reading is always off. Yeah, so 11 11.4 Our battery's dead inside the vehicle. but we should still have a good reading here. Okay, so we're five volts.

We're adding money. five Point Zero zero actually ground side about five millivolts so that's interesting that I Thought that would have went a little bit. High Let me just go across the two terminals here and just see using the center ground if our five volt is pulled down a little bit. that 5.00 4.99 Boy, that's so interesting.

The fact that we have five volts and we're reading 10 degrees off? it's reading 77 degrees. 78 degrees of course I just touched it. So it's going to change a little bit. but I'm sure if we, well, we still got our little digital one out here.

it's probably 69. See, we'll wave it across here. Make sure we hit her a couple times. Yeah, this is reading 59 degrees.

That's saying it's 78. foreign Copper says it's 62 in here. 63. The fact of the matter is, it skewed more than 10 degrees, but we have a steady 5 volts feeding it.

Let me. uh, let me think on this one here a little bit. folks. this is pretty bizarre.

It's pretty bizarre. Like, is this a bad PCM Um, we're looking for a decrease in resistance in the circuit. We can look up the resistance value of the coolant sensor as far as what resistance value is is supposed to be what given temperature age. Sometimes they're not very specific.
It's usually a range. um, so we can look at that and then if we have a known resistance value in the circuit, which we do, we can measure the resistance of our coolant sensor and then we can measure total circuit resistance from the PCM Wherever it lives, this thing's got a V8 in it, which is kind of bizarre. The PCM lives right here, so that's easy enough to unhook, pull up, and check total circuit resistance of the coolant sensor circuit to determine. Is it good or is it is there a connector that has some green crusties in it which I would assume if it did.

if a connector had green crusties, um, our open circuit voltage would not be good. it would be less than five, which it goes from 5 to 4.99 Is that I mean we might only be looking for an Omer two? I'm just talking out loud here. Let's gather some data be be more equipped and then like I don't know an old gas will get after it. So I'm confusing a couple things.

I I Still think they go to the minus 40. So that's kind of weird. but the fact that they both went to Minus 38.2 whatever it was. Anyhow, I found the chart of resistance Trailblazer EXT Which is what this little guy is.

It's 68 degrees F it's 3520 ohms 3.52 kilo ohms. It does give us this little chart. It's odd that the Trailblazer 26 oh no. I guess they're both the same so they're both the same I Guess it really doesn't matter.

Um, although at least I I mean they use the same sensor, why wouldn't they be the ex and EXT who cares? So we do have that. we have that. and then I Grabbed a OEM diagram here and we can see that the wires go. the only connector is the connector at the coolant sensor.

Other than that, the wires run straight to the PCM I'm not familiar enough with internal printed circuit board stuff to know you know how the PCM calculates. You know everything coming into it. I Wish I did. but I don't.

Um, so let's see what our resistance value is and see if we can put a known resistance value in it and see is it skewed? You know, approximately 10 to 14 degrees from? Well I've got a variable resistor. Let's set it up at 3520 Ohms and plug that little guy in 3.520 kilo Ohms 3520 Ohms which is supposed to be whatever it said there on our chart. 68 degrees F So let's take and unplug this. I've got a couple probes here.

Probably grab the wrong size. No, I didn't I Grabbed the right size. first. try.

See, there we go. So we've got 35 40 in there. Let's grab a scan tool, turn this little guy back on. Look at that.

68 degrees F Right on the freaking notes. Did we get a bad coolant temp sensor? Are you kidding me? Are you kidding me? Napa 35 20 is supposed to be 68 degrees? Well, what is the freaking odd to that? The one that's in the head Junk. This one appears to be junk. Let's put it at uh oh.

let's go to 158 degrees. Well, we'll take it right up to 212. 177 Ohms, Let me reset this thing to 177. we'll just check a couple ranges here and I think we'll be in good shape for the shape we're in.
Ain't that something? I wonder if that guy shops at Napa too? So let's keep cranking our resistance down. Oops, It's hard to get things on a low scale on this thing here. Let me just get them. Oh, we're really close.

Well, no I thought we were. It gets kind of fiddly at the lower end of the range here. Oh, there we go. We're 170 178.6 so this should be close to 212 degrees.

We're within an OHM oh my. God Well, two 208. and I was looking for 212, but we're in a very finicky portion of it. I'm going to go up to a higher reading we're going to go to 7280 ohms because that's a little easier to fine tune.

I'll get that tuned in and we'll see what that reads 7.28 kilo. Ohms. and according to my chart, 7.28 should be 41 degrees F 41 degrees F Right on the nose folks. Freaking.

Napa Almost sent us on a wild goose chase. Wow. having me really scratched my head I Knew it was a possibility, but gosh, what are the odds of both of them being broke? Very, very similar. Uh, so these are made by standard Motor Products And the problem is.

problem is folks. I Don't have any other vendor that sells parts around here that doesn't sell either Napa or standard Motor Products I'm about to see if I could order a Delphi one or maybe the Chevy dealer has one in stock. Let's just see what resistant you ain't gonna believe this though. you ain't gonna believe it that doesn't plug in there.

What's up you need me? Uh-huh? Okay, stand back folks. Touch it here. But let's just see what our resistance is here because it seems that the computer and everything functions as it should. Our resistance is the point Six Nine, 2.7 kilo Ohms then on our chart anywheres? No, it's not, but hoping we can find it in between.

I Wish they had a chart for every temperature inch, but they don't But this is a good chart because this tells us that the computer is spot on baby. Um, I Don't know if this works in a linear fashion. If you can calculate the resistance value for each temperature, it's neither here nor there. I've got enough data to condemn a new part.

Why? I Wasted a lot of my freaking time or enough of my freaking time. But we should have known we shouldn't. No, we should have followed our facts because our open circuit voltage is 5 volts. If we had any resistance in the circuit bringing that voltage down, we would have seen it.

We should have known right then and there that our coolant sensor, albeit brand new and all be that one brand new, must be junk. Well, I Guess that's it All right folks. I Know it's almost lunchtime now, so quite a bit of time just passed. Let's see here, we still almost gonna slip the key on.

Continue to put the maintainer I Gotta say, uh, a Delphi sensor. the other Napper had one of these I didn't see any sense of getting one from Fast Freddy's or from Advanced because they all carry, you know standard Motor Products So which I double checked with Napa and that's what you know. that's what Eclined is. So let's take this little fella see if this values any different.
Chevy Garage Do Not have one. Let's plug that in and let her sit here in outer space. I Think we're probably doing better already. Of course the furnace has been running in the shop, but we can see our intake error is 71.

and our coolant is sitting there at 68 now. I Guess we can grab our little temp gun there and see where we're really at, so that's where you guys can see it or not, but maybe I'm just going to hold that here. We'll touch this here and then. okay, not to touch the sensor itself.

It says we're 64.4 so 64 and a half and it says here 68 So we are a heck of a lot closer than we were. that's that's for sure. he's touching my fingers. make sure it's responsive here.

73 Told me with my hands, so it's at 75 just touching it with my fingers. I'm going to take my fingers off and just see where we're at out here 68.7 according to Scan Tools 73. it's going to be a little different here from the inside outside where the actual temperature probe is, but it looks like we're only about four to four degrees skewed from what we see here versus what that actually is, so that's good. We're definitely on the right track now.

I Expect there to be some variants, but it's when our variance gets up in that 15 18 degree range. That's that's no good dude. Um, I'm gonna take and put this sensor in the head and then we're going to see what we have. This plug, wires reach down here a little better I Cracked it loose.

It does have blue goo all over it. You know? we're probably going to lose a little coolant here. hopefully not much caps on it. We're losing a little bit.

Let me get this one back in there before we lose too much. So I remember the Napa sensor had blue thread Locker on it. This Delphi one has white I Don't know if there's going to be any identifying marks. Yeah, there is.

It says 2207 on the side there. We'll compare it to the one we got from Damper, because maybe there is. Uh, maybe there's an issue with the calibration of the aftermarket there I Would have liked to have gotten a an Oem one, but we're gonna see how this Bell pie works out For what it's worth is about twice the cost of the Eckland one. so we'll get this snugged up.

It's just about lunchtime, so I'll let this thing sit out here with the furnace and stuff off and kind of let the temperatures all neutralize and we'll see where we're at with Ambi air. Tempting because the Ambi air temp would be a little higher than the hood because the furnace is just above us and it blows right down here under the hood, so it might have that kind of goofed up for the time being. so we'll snug that up, we'll get our socket back, we'll take in the get it plugged in here and then we'll see just kind of where we're at. Baseline must be somebody else was already perhaps in this, you know, on this path and then maybe gave up because you know, why else would it have a new sensor and a new connector? So I'm thinking that somebody else may have seen this what we're going to do but I just didn't know how to go all the way taking it all the way folks.
Let's see if we move this camera so I can see so that's reading 55.4 degrees inside that cylinder head right now. 71 on ambient air temp. Let's just shoot the cylinder head so it'll cylinder head I'll just kind of get all around here. kind of get the average.

So the max value has been 57.7 degrees and it says it's 55.4 and as I move it around here, it's 56 58 59 depends on where I go 52 53 so that seems right. I'm happy with that folks. Okay, lunch is over. That's kind of annoying.

You guys are going to deal with it for a minute. It must be the rear. Uh HVAC Okay Engine Coolant Temp Air Temp show selected. you can see we now have it fixed so to speak.

So it's been sitting outside here for a while. They're within a couple of degrees of each other and this is what we expect to see now. I'm going to start the vehicle I'll turn you guys off because that'll eventually quit clicking I assume I don't know where you turn. uh, hopefully it quits clicking that quick click and finally I've pulled up some data on the screen that I think is important to watch.

I'm going to graph the coolant temp I Know it's kind of hard for you guys to see out here. so I don't know what you're gonna see but our Loop status I'm gonna look at our field trims engine RPM Vehicle speed sensor, intake, air attempt you know airflow rate from the mass airflow and then we're going to look at the oxygen sensors and just kind of see how things are working as we've taken out a test drive. uh, waiting for it to hit closed loop operation here. and then we'll go for a rep and see if this thing wants to run it's Catalyst monitor.

Hopefully it will. So initially to take off, we're just driving it easy. you know? No. Full Throttle accelerations and on a GM port to run the Catalyst monitor, it has to be driven for at least 10 minutes continually.

And if I remember correctly, you can actually run this test. uh, in the shop, put open foot on the brake, uh, in park I believe And then you run the engine essentially for 10 minutes above 2000 RPM Something like that. After 10 minutes, let off the throttle, keep your foot on the brake, put it in drive, and then what it does is a very similar test to what happens when we're driving down the road. Um, it's going to force the system rich and then it's going to force the system lean and then it checks it, checks for oxygen storage capacity in the converter at that time.
Um, I Believe that's how they run their past. Oh great. We better not get freaking pulled over here because we got no inspection on this thing that's 5-0 right there. Nope, He's got better stuff to do that's good.

Um, so when you're driving, you drive up for 10 minutes, at least 10 minutes, get the engine fully warmed up, and then we accelerate, drive it for a steady two minutes and then pull over and stay pulled over with our foot on the brake and you should be able to watch it on scan data of course. Rich force it lean and then it's going to compare action storage capacity. but I think it also looks at the index switch ratio of the rear. O2 sensor I think I've got positive on that but I'm pretty sure I told Gdf works.

but what they do the catalysts that's I think it's a little different so we'll see I'm gonna drive it, we'll get it warmed up and I'll and for what it's worth, I'm just looking at O2 sensor data. I'll tell you right now this is going to throw a PO420 into Po430 because neither one of these Cadillac converters are working at all. Not even like a tiny bit. So the Batman I'm going to say we're going to throw a Cadillac converter codes down.

So while I'm thinking about it, that can be the The Dilemma or a dilemma can be with your customer. You know they take them to their shop which this guy has. He's got a you know a ran out 10 day up here from another shop. They failed it because they didn't run the monitors.

They don't know why it comes to you. you fix it. so it runs the monitors but now you know you got an engine light on. You got all these codes.

So I try to be transparent with my customer to tell them like look, you know I fix your car. it should run the drive cycle now. However, because it can do that, the systems can test themselves and you potentially could have you know an engine light on it. So same thing that Buick I think I told you guys about earlier that fix the drive cycle on that.

of course you know I came back with the EVAP light on. you know engine light on for you have problems and everything else so but that customer was was pretty well aware of what I was explaining to them and half expected his light to come on. and it did. So we fixed it and the way we went say looking at data there I would be flabbergasted.

it just doesn't have Catalyst codes. Gosh and it's another cop. Let's see if he pulls us over. he's on the brakes.

He's been on the brakes hard. uh yeah, he's looking. oh man, he's like just stopped. Maybe he's gonna whip around the roundabout and come get us that way.

pulled right over. But let's see. I'm pretty sure this is expired, expires 119. yeah, we're inspired by like months.

I've been driving a little longer than 10 minutes here. I'm gonna pull over here. we're gonna wait just a second. then I'm gonna accelerate.
You know, throttle? We're gonna drive steady for at least two minutes and I'm gonna pull over to the side of the road and let it sit there. and then I'm gonna watch How It's scandinated and see if we can watch it run. Uh, the Catalyst monitor. Hopefully we get to see that.

No promises. but hopefully so if you're driving, it should be along and you're you're watching this yourself. These are the data pitch you're going to want to watch you see all four of the O2 sensors and then your air fuel ratio pit. Because like I said, you'll watch the PCM change the air fuel ratio when we pull over and we're idling in gear.

If all the other parameters are right sometimes, but not always the case, but hopefully it works for us this time we've met all the other criterias, pull over, and then we're gonna watch the scant out of here. So just pull over. make sure you keep the car in gear, idling your foot on the brake too. If you met the criteria, hopefully it'll do it.

Usually it does it within you know, 30 seconds of pulling over. So yep, so just force it there. You can see it in O2 sensor data. We're back to 14 to 1 air fuel ratio so it happens that quick and that's when it passes judgment on the converter.

Okay, so now what we can do, we probably gotta do it a few times. I think you do it two or three times. We'll see if it has any pending codes. Yep, so we've got a fault code already.

We probably have a pending 420. uh oh nope. that was uh, engine coolant from freaking around with that uh, you know, no engine light? Of course let me just pop into generic OBD2 I Went back to the OEM so we could see the air fuel ratio PID there. Um, so we're going to pop in the back into class two data.

so J1850 on this one. let's just see here for getting some giggles. I think just that one pass. it does not run the Monitor and did not throw a pending code.

So I'm gonna go do this again. And there it is baby! The Magic Money light got it on my second track here. We'll uh, pull in up here at the park and see what code we have and that's what we were hoping for. So that is a big green light for us here.

In this case, you got a light saying that, hey, you fixed it fella. But now you got other issues. So let's pull in here see what what we have for codes. We had that one for coolant, but I'm assuming we have one for uh Catalyst Now Yep There we go.

Cal's efficiency bank two. If we keep driving it, it's gonna throw one for Bank One I Guarantee it. So this code we generate I don't know why that doesn't show up in uh, generic data. That's kind of concerning.

However, we got a Po430 which I made that call before we even started. Well, at least we can give it back to our customer now and tell them like hey, we fixed what you wanted us to fix. Oops, Come here because that's what we were hired to do. We were hired to uh get the drive cycle to run and you can see now.
it has ran the Catalyst monitor so obviously couldn't set the code Catalyst monitor. Okay, so we fixed uh his problem but he's gonna have to keep driving I'm not gonna drive it till it runs the EVAP system at this point. I'm happy with everything. Yep, we got a current and a pending Po430, but I bet you dollars a donut said it's going to throw a 420 also because neither one of the converters work at all.

So and I haven't looked underneath I Don't know if he's got spacers on them or anything like that, but at this point, not my problem. We did what we came to do. So that's it folks. Hopefully you guys, uh, get some value from this.

You know? ultimately the end, he has engine lights on. He's going to have other codes here. It's going to have Evap codes you know once that monitor runs. but hopefully you gain some value of seeing.

You know what are we going to look at to make sure this is just one little tiny aspect of of a drive cycle on a GM I'm quite familiar with them and you know like I said I've seen a host of different things cause drive cycle snap to run. most popular on General Motors is coolant related issues that that variance of not getting a cold start whether the intake temp sensor skewed or coolant temp you know and in this case you know a bad new part. two of them, the one that was in it plus the one we have and it looks like somebody was probably on the right path with this, but they just didn't know enough to stick to their their diagnostic process if they had one. I mean they could have been just shotgun and parts and I don't know.

but if you're looking at the values on your scan tool, substituting a known good value and seeing what you need to see, then in our case like this, it could be nothing other than a failed coolant sensor and then knowing how to run the drive cycle or a very particular part of it is also handy too. like I know how to run on my GMS for the Catalyst Monitor and we got it. You know on the second go around got it to throw a code which you know we knew it was gonna just just by looking at data I can tell you this thing ain't going to pass. callus monitor.

That's another story in itself. a story from you and I want it in that comment section. Along with your questions, your comments, your concerns, find us on the socials. The Entity The Facebook You guys know what to do and just remember viewers.

If I can do it, you can do it. Thanks for watching foreign.

99 thoughts on “Chevy trailblazer: will not run a drive cycle”
  1. Avataaar/Circle Created with python_avatars HvDc5Knight says:

    Napa is garbage, had 2 bad alternators for a vw and finally customer agreed to OEM and that one worked

  2. Avataaar/Circle Created with python_avatars Bill Doodson says:

    What is a drive cycle?

  3. Avataaar/Circle Created with python_avatars digitalwoodshop says:

    Wow…. Excellent Video.

  4. Avataaar/Circle Created with python_avatars Dj Martin says:

    Glad you were able to take us along for that one. You are legendary my guy

  5. Avataaar/Circle Created with python_avatars Haslet Joe says:

    All I can say is AMAZING! No, not the car fixing, that you married Mrs. "O"! Just kidding, I love the even temperedness and calm cool approach. Do the troopers actually give you a ticket? PRNY in action. Love the videos, terrific content and wonderful folks. And Mrs. "O" might be a keeper too! Thank you…

  6. Avataaar/Circle Created with python_avatars Steven Resendiz says:

    Okay I fixed it, the check engine light is on

  7. Avataaar/Circle Created with python_avatars Alan Earnest says:

    It seems to me these last few years that aftermarket and oe parts have gone down the tubes

  8. Avataaar/Circle Created with python_avatars Rod kennedy says:

    Keep em coming Mr O. 👍🇺🇦👍🇺🇦

  9. Avataaar/Circle Created with python_avatars Donald Perrin says:

    watching the O2 data showing it test the cats in real time was neat, reminds me of when I had a cat replaced on a buick to rid the 0420 code. few months later the light was back for the same thing. ended up watching the data while I gave er the beans and the rear sensor settled down. I just let it clear the light on it's own to be sure it was cleared.

  10. Avataaar/Circle Created with python_avatars Christopher Rodriguez says:

    Hey Eric just wondering could you make a in depth video on the autel scanner ( functionality,tips and tricks) or do you have any video recommendations?

  11. Avataaar/Circle Created with python_avatars George F says:

    Always good to save a v8 trailvoy

  12. Avataaar/Circle Created with python_avatars David McClain says:

    Great information and diagnosis on this one. Great job.

  13. Avataaar/Circle Created with python_avatars Buck Roger says:


  14. Avataaar/Circle Created with python_avatars lizard2006 says:

    Advance carries NTK and Acdelco.

  15. Avataaar/Circle Created with python_avatars Michael Williams says:

    The worst engine is the 4.2 L oil pump went out at 110,000 miles oil changes every 3000 miles good oil. At least that one has the 53 LS.

  16. Avataaar/Circle Created with python_avatars Good Time Johnny says:

    Sometimes the part store will send you what there computer tells them to. I take the OEM part number and when I cross reference it I usually get a different number than the one they send me. What I'm trying to say is certain parts may fit the application but are not calibrated to the vehicle.

  17. Avataaar/Circle Created with python_avatars Baz W says:

    Love these videos of proving that new doesn't mean it's good 🤙 great diag and hopefully another happy customer, all the best 💙

  18. Avataaar/Circle Created with python_avatars tinkerwest says:

    New parts turning out to be NFG has become all too frequent…I feel for ya partner…

  19. Avataaar/Circle Created with python_avatars Mike TeeVeeDub says:

    A couple of years ago I bought a Standard MAF for my Ford when trying to diagnose a P171/174 lean error. I immediately got a sensor failure message upon installation and subsequent drive cycle . It went away when I put the original Motorcraft MAF back in.

    I learned a valuable lesson that day. Even if the part is new, it can be crap. Thanks for reenforcing that message Eric – buy OE parts whenever possible folks!

  20. Avataaar/Circle Created with python_avatars Bill Chadwick says:

    Eric, I am one of your big admirers, but when you unplugged the sensor and the reading went to the lowest value you then knew there was no partial short in the wiring, which is the only thing other than a faulty sensor that would give you a false high temperature. Also, the "crusties" on a connection would have caused a false low reading, so not a possible cause.

  21. Avataaar/Circle Created with python_avatars Patrick Williams says:

    Eric!!! Where can I get this variable resistor tool?

  22. Avataaar/Circle Created with python_avatars Jeffrey Evens says:

    Very thorough step by step diagnosis. Nice video, very informative!

  23. Avataaar/Circle Created with python_avatars Steve Ashcroft says:

    would the open circuit voltage have been anything other than 5 volts, as no current flow = no voltage drop? So would you see less volts with a multimeter if there was a resistance/green cruddys in the circuit

  24. Avataaar/Circle Created with python_avatars Joe Dantuono says:

    Good tip about just plugging in the coolant sensor and scanning if it's close to ambient temperature!

  25. Avataaar/Circle Created with python_avatars Chris Zimmerman says:

    If this was a first time this owner had a NY vehicle test on this vehicle he may have uncovered a way to keep the MIL off by an unscrupulous seller.

  26. Avataaar/Circle Created with python_avatars Paul T says:

    We had a 2010 jeep TJ wouldnt complete drive cycle due to 02 heater not completing after new 02 sensors but the people wouldnt bring the vehicle to me to check it out
    Getting to a time in my life after being retired for 13 years bring the vehicle to where to tools are or i dont want to look at it

  27. Avataaar/Circle Created with python_avatars Sciatl says:

    Delphi was GM ome supplier for some parts

  28. Avataaar/Circle Created with python_avatars J. Hart says:

    I love watching you and your testing equipment go to work. Reminds me when dealer could not tell me why car would shut down after 10 minutes of running. Always happened to the wife never me until 1 Sunday morning. Waited 15 minutes cracked right up, got it home, got my Dodge engine book and voltmeter. It was an 84 Dodge caravan, 4 cyl.; there was a motherboard inside the distributor for lack of better name. When it got hot it would crack, when it cooled down it made contact. The dealer shouldn't have found it in 20 minutes, took me 4 hours and a bunch of fancy words directed to Dodge.

  29. Avataaar/Circle Created with python_avatars Randy Hawke says:

    Like I've heard you say before: "NEW" stands for Never Ever Worked…. So true…

  30. Avataaar/Circle Created with python_avatars Eliminator 19 says:

    Use a cup of ice water to test the sensor. Should be right at 32. A trick my dad used to verify his thermometers back in the day.

  31. Avataaar/Circle Created with python_avatars JAXTRUX says:

    This is so much better than politics lol,,, I learn something every video thanks Eric, some of us are paying attention!

  32. Avataaar/Circle Created with python_avatars Nik Mitchell says:

    I have a similar experience with my 01 Silverado – failed knock sensor circuit code, which is already a bunch of work to get to. Checked my AC Delco replacements on the ohm meter, seemed legit? – put it all back together – SAME. CODE. More than likely one of them was still off somehow. I haven't gone back to fix it again. 😛

  33. Avataaar/Circle Created with python_avatars Franklin Cormorant says:

    Nothing but problems with Standard parts: oil pressure senders, temp sensors, MAP sensors, etc so often out of calibration. So much wasted time diagnosing phantom problems because "it can't be the new part." Use dealer parts, Bosch, Delphi, Denso, NTK/NGK. Cheap parts that don't work are worth $0.

  34. Avataaar/Circle Created with python_avatars Melanie Branton D.V.M. says:

    Eric, I know you would not do this but is it possible for the owner to put spark plug foulers on O2 sensors to stop the check engine light due to catalytic converter issues. Of course this suggestion is coming from Mississippi which does not do an emission test; otherwise, 75% of the vehicles would never pass.

  35. Avataaar/Circle Created with python_avatars Wildman93 says:

    I had that same problem with my ford 12 or so years ago junk new napa sensors. got one from the ford dealer worked haha so from then on I dont use any aftermarket ones. crazy how picky the specs for calibration are another great video from you man cheers

  36. Avataaar/Circle Created with python_avatars gregd393 says:

    after market nock sensors do the same thing. Throwing codes new out of the box. Good Job!

  37. Avataaar/Circle Created with python_avatars John Bragg says:

    Sherlock Holmes is alive and well in Avoca NY.

  38. Avataaar/Circle Created with python_avatars Leo Curious says:

    You cant measure shiny/bare metal with an IR gun. All you will see is whatever is reflected off of the metal. Its like trying to look at a mirror: All you see are reflections.

  39. Avataaar/Circle Created with python_avatars Russell Bomgardner says:

    big help for me Thanks Eric . my 06 chevy express 3500 has been giving wacky engine temps for a couple years. I replaced the sensor and still the same. You gave me a lot of great insight and info. I really like watching great diagnostics at work. You da man😉

  40. Avataaar/Circle Created with python_avatars Robert Van Blair says:

    maybe it is minus 40 degree celsius (Wink Wink Wink )

  41. Avataaar/Circle Created with python_avatars Danny Cole says:

    Had a problem with a dodge that wouldn't run O2 monitors. Swapped out all the 02 sensors ( had universal Bosch) with factory 02. Monitors all ran. It was on a challenger. I don't remember the exact details as it was about 2 years ago. But if you are interested, I saved the files on it.

  42. Avataaar/Circle Created with python_avatars ExittOnly says:

    That crimped on butt connector, on the ECT sensor would have immediately, been my first suspicion. Those should never be on ANY sensor. They must be soldered and heat shrinked. Not doing so more often than not, adds excessive resistance to that circuit.

  43. Avataaar/Circle Created with python_avatars Bobby Tectalabyss says:

    Hi Eric. I was re watching some videos you did 8 years ago. You seem a lot more comfortable with pootube. Only reason I am still here is channels like yours.

  44. Avataaar/Circle Created with python_avatars jimbo W. says:

    A fine example of the bowtie circus.

  45. Avataaar/Circle Created with python_avatars A. R. says:

    Job security.

  46. Avataaar/Circle Created with python_avatars BrainEnwrong says:

    Wow. As a mechanic, I would’ve been further down that rabbit hole before thinking the new sensor was bad.

  47. Avataaar/Circle Created with python_avatars Hola! anonymuswere says:

    one thing I've learned from watching all you repair guys (you, Pine Hollow, watch wes, and Rainman ray, even a little Adept Ape) is that OBD2-equipped cars basically need OEM electronics and sensors or the computers can't read anything correctly. also, if I'm reading you correctly, all you need to do to spot a shot cat(s) and/or Oxygen sensor(s) is to look for 420's and 430s?

  48. Avataaar/Circle Created with python_avatars Adam Trombino says:

    New part performance verification, is never a waste of time!!

  49. Avataaar/Circle Created with python_avatars K B says:

    I’ve diagnosed a handful of “won’t run monitors” cases because I only worked the last 5 years of my career in emissions testing areas. I can say without any hesitation that maybe 5% of the mechanics out there in the field can accurately diagnose these problems. They require the most complete understanding of how fuel injection and emissions control systems work of almost any of the engine diagnostics jobs out there and can throw off even highly skilled diagnosticians. The industry is short on quality techs but it is critically lacking on quality diagnosticians. If you’re a shop owner and find a really good diagnostic tech, hold on to them for dear life. I left the industry because I was tired of being underpaid and under appreciated. I could make more money as a mediocre electrician than I could as an excellent automotive diagnostic tech.

    I ran into a similar but different issue years back on some sort of GM product. I think it was a Cavalier. The factory PCM was misreading the TPS. The PCM showed the TPS as being like 0.3 or 0.4V higher than actual, which pushed the closed TPS reading outside of what it considered closed throttle, leading to it keeping the IAC open all the time for dashpot function. Tested it all the way back to the PCM pin itself and the voltage the PCM was showing was consistently higher voltage than the actual voltage read by a DVOM. PCM power and ground was good, shotgunned a PCM in it and fixed the car. Original PCM and TPS.

    Can’t say how many times I’ve gotten aftermarket sensors that read incorrectly. It seems like the cheaper, easier to manufacture sensors are more likely to be junk. I’ve had so many defective aftermarket brake light switches. It’s a freaking on/off switch, and yet the aftermarket can’t get them right.

  50. Avataaar/Circle Created with python_avatars Todd says:

    I’ll tell you my story…one time years ago I had to fix my vehicle and did a search on YouTube. Amongst the results was a SMA video on exactly what I was needing to do. I watched the video and subscribed due to being able to identify a diagnostic Guru when I see and hear them. I’ve watched countless videos since and not one of them did I need to watch for anything I was doing or needed help with. The reason I have watched all the SMA videos is due to not only is E a whiz at diagnostics, he is a genuine good mechanic and just as importantly….good people. Oh yeah and he’s got a really good sense of humor. I’m enlightened, entertained, and have learned more than I could have ever imagined.
    This channel is without a doubt one of my very favorite.
    Luv me sum SMA

  51. Avataaar/Circle Created with python_avatars Robert McGraw says:

    FYI don’t forget how inaccurate that thermocouple and IR gun are. Think about getting a Pt RTD if you want true diagnostic accuracy.