O2 Sensor Code? Don’t Replace Anything Until You TEST This!

Added: 2026-05-19

[00:00:00]All right, guys. Today we got a 2006 Dodge Durango with a 4.7 liter in it.

[00:00:05]This thing has two O2 sensor heater codes that come back just like that. Is it two bad O2 sensors or is there something else wrong with it? Let's get into it.

[00:00:17]Couple things we're going to do in this video. One is we're going to show how just because you have two codes for two different components doesn't mean that we're always going to have one single thing bad. We could have two bad components. We don't know. or we might have something singular bad one part.

[00:00:32]And guys, hang with me on this thing. I am feeling really like run over poopy right now, but I feel like this is important for everybody to know. So, we're going to I'm going to power through this, get you guys some good information, and then I am going to head to the homestead. All right. So, we're going to figure out I'm going to show you guys how do you test this because an O2 sensor heater code is a very common code that we see and it's different from a just a regular O2 sensor code. So, you might have an O2 sensor, performance code, circuit code, that you have a sensor side, and you have a heater side, all built into one O2 sensor. Let's start off with showing you the There's no codes in here. Right now, we've got the the key is on. If I go over in here, I hit read codes, there's absolutely no codes. What I'm going to do is I'm going to cycle the key if I can breathe.

[00:01:22]I'm just take the key, cycle it off, cycle it on.

[00:01:29]Where did the wipers went?

[00:01:32]Let's go back and read those codes again.

[00:01:39]There we go. Both those codes pop up just like that. All right. You might ask, well, why weren't they there before? Well, we cleared them and left the key on. And that's something you have to remember. You clear a code and you don't cycle the key, it may not set that code again until you cycle the key.

[00:01:56]What happens here is every time that key is cycled off to on, the engine module runs a test on those O2 sensor circuits.

[00:02:03]And there's four O2 sensors in this vehicle. And it's going to run a test on all four of those O2 sensor heater circuits to see if they're doing what they're supposed to be doing. If they're not, it's going to throw these codes.

[00:02:13]So, we have both rear codes. And the reason we know that is both of them say that says bank one sensor two, bank two sensor two. All right. Both rear O2 sensors. Now, I'm going to tell you, when you first get into one of these, a lot of times, a lot of GMs are like this, but a lot of vehicles are like this. A fuse generally feeds power down to those O2 sensors on the heater side.

[00:02:38]And the engine module cycles, duty cycles, the ground side to heat it up.

[00:02:44]But don't assume that because let me show you the wiring diagram on this one.

[00:02:49]On this one, we can see we're going old school today, guys. You can see we have a ground here. And now we have three O2 sensors here. Here's the other O2 sensor. Okay? And we can see if we look at these, they all share the same ground. All four sensors share the same ground. So, you see I have that highlighted here, right? They all three come over and go to G 100.

[00:03:13]And this one also goes to G100. Now, I will tell you G100 is extraordinarily difficult to get to. I mean, it is buried at the very back of the motor at the top on on the passenger side.

[00:03:27]Incredibly difficult to get to. And the reason I say that is a lot of people would say, "Well, let me go ahead and get to that ground. Let me let me clean it and tighten it up." Yeah, you're going to spend a few hours getting to that ground and taking it off and cleaning it and tighten it up. Not going to do you any good. And some people would say, "Well, yeah, but it would affect all four sensors." It could, but it could potentially only affect one or two. It's possible. It's just not the way to go about your business. This is not the way to test something is just to pull it off, clean it up, and put it back on. Let's see if the ground's the problem before we go after that.

[00:03:57]Especially when it's buried like that.

[00:04:00]All right. The other circuits that we see, so if we're looking at an O2 sensor, I want you guys to look at this.

[00:04:06]Let's just look at this one. And you can see that this side of the sensor is our sensor side. See how it's got the little arrow there? And that would almost be like it's a little arrow that moves like that. Okay, that I mean that's kind of the the how I think about that symbol.

[00:04:22]This side, as you can see, looks like, if you think about it, like a rear window defro defrogger def fogger. So, it's got it looks like a heater circuit, right? So, this is our I'm going to cover up the other side.

[00:04:37]There's our heater side right there.

[00:04:39]That's all we're worried about. not worried about the and I always tell you guys I like to break wire diagrams in half. I am not worried about that sensor side whatsoever. All I care about is this side on that one and this side on this one. Right? That's our rear ones.

[00:04:54]Yes, we have grounds that go over to the same ground from those two sensors. And then the other two circuits that you see I've highlighted there, they just go to the engine control module. These two circuits, you just have to trust me otherwise I'm going to be pulling this thing all over the place. They go to the engine control module. So, where I said a lot of O2 sensor heaters are controlled, they have power going to them through a fuse and they have the engine control module cycling the ground. On this one, they're grounded all the time and the engine control module puts power to them, cycles the power to them. Okay? You have to know that because when you go to test this thing, you need to know how does it work. If you know how, if you know why, you can fix it. We know how it works.

[00:05:36]Now, we can fix it. All right, we've got our maintainer on it. We've got our our scope set up. Let me show you what we got. I'm also going to use a meter because in this case, we're going to do an ohms check on something. I'm going to show you how to find out how many balls we should turn on this. And I'll show you why we're doing that. Let's get this vehicle up in the air. And let's take it to the next step here. Real quick, guys, if you're not already subscribed, which a lot of you are not, jump down there and hit that subscribe button. When we get to 500K, we're only 25,000 away.

[00:06:04]When we get there, massive giveaway.

[00:06:06]Back to the video. Let me show you where we got the scope hooked up. So, we are on the left side rear O2 sensor. Okay, we're up here and we are in the heater circuit wires. We're back probed into the heater circuit on this side. Again, we've got the other two wires are for the sensor.

[00:06:29]These two wires are for the heater. And that's what we've got the scope. So, we've got the yellow and the red lead of the scope connected to that. Now, here's the thing. I'm going to show you how you don't need a scope. A lot of people say, "Oh gosh, you go right to the scope."

[00:06:44]I'm going to show you how you don't need a scope to check this, but I just want to show you the pattern that we got. You know, you guys know that I'm going to put a scope on it just so I can see what the pattern looks like. I'm going to show you how we're going to make a pattern. We're going to go into into the scanner and we're going to go to active test.

[00:07:01]And you should be able to do this on most scanners. And then we're going to find, you can see we've already been in it. O2 sensor bank one, which is the driver's side, rear O2 sensor. Let's go into that.

[00:07:14]And then we're going to just I'm going to put it at 25%. Because like I said, the computer is going to duty cycle.

[00:07:20]It's going to turn the power going to it on and off, on and off, on and off. All right, let's start the scope.

[00:07:27]Let's tell you what, let's turn the green and the blue off so that way we're not confusing anything there.

[00:07:34]All right. You can see we got a little little bias voltage on the yellow. And you can see that the red is sitting at ground. Let's turn on the And there we go. Now the computer is activating that heater circuit. And I can tell you from looking at that that that doesn't look good to me.

[00:07:50]It's not pulling all the way to ground.

[00:07:52]If we get our cursors and we come down to the bottom of this right here, you see that we're still sitting about 3 and 12 volts.

[00:08:02]That's really not. You want that thing pulling the ground. I mean, it's may not get all the way there, but it should get pretty dog on close to it. The other thing is it looks kind of funky. If we zoom in on it, it's just a really weird looking pattern with this. It's not pulling this to ground. And then you got these little spikes that come down. This is really how far it's going is right here, which is 8 volts. And come over here. So, again, doesn't look good. All right, let's turn that off. You don't have a scope. You need to know if this thing works. You need to know if it's what's wrong with this car. Am I putting O2 sensors in this car or Right. First of all, let's look at our ground. I didn't do that. I should have I I got a little ahead of myself there.

[00:08:46]Is our ground good?

[00:08:48]Let me see if you can't see it here. Can you let me panhanded? I'll pull it up.

[00:08:51]Sherwood. Here's our ground. It's activating right here. And the ground is sitting dead on zero. The ground is good. I'm not going after that impossibly difficult to get to ground.

[00:09:03]The ground is fine. All right. Now, we need to figure out how to fix this thing. But you don't have a scope. And you want to know is the ground good. You want to know if the if the O2 sensor is the problem or if it's the computer because that's the only other option here really is is the computer able to activate it and and pull it to ground and do what it needs to do. Maybe power and ground going to the computer. If it before you condemn the computer, that's where you would go. But let's test it.

[00:09:27]Let's use some simple tools that you can buy. You can get one of Joe's load boxes. You can get another load uh box and you can test it. How do we know how many light bulbs to turn on? Here's a problem. We have anywhere from 2 and 12 amps to 15 amps. We don't want to put too many. That could be a big problem if we put too many. We don't want to put too little, right? We need to put something that's, you know, that's going to simulate the sensor. Here is a new O2 sensor. We can take a new O2 sensor and you should be able to find these specifications online, but you can take a new O2 sensor and you can measure the resistance of the heater. Let's do that.

[00:10:05]So, I've got my meter here and let's go in and I'm just going to back probe the the heater wires. You see, we have four wires. These are for the heater. And how many ohms do we have? 3.5 3.6 ohms. All right. So, we have 3.5 3.6 6 ohms of resistance on this heater. Now, we know how many volts are going to roughly be in this this car, right? This vehicle, even if we take base battery voltage, even because when you cycle the key on it, test this thing. So, all we need to really use, let's just use 12 1/2 volts. 12.7. Yeah, with the engine running, it's going to probably be 13 and a half, maybe a little more than that. That's okay. If we just take 12, easy math, we can use Ohm's law.

[00:10:49]Very simple, right? voltage. You're either going to if we know the voltage and we know the resistance, which we do know that, right? So, our voltage we're going to go with 12 and a half and our resistance was 3.5.

[00:11:07]And all we need to do is divide that into that. Now, I will tell you right now, I don't like math. My wife's the math teacher. I don't like it. So, I use a little Ohm's law calculator that you can get on in the app store on any phone. And if you put in those numbers, we're going to put in 12.5 and we're going to put in the resistance at 3.5.

[00:11:38]Our amperage is roughly 3.5 amps. So if we know those two numbers, these are going to this is going to be roughly 3.5.

[00:11:49]Easy, right? All right.

[00:11:52]Now, we know that this is 2 and 1/2.

[00:11:54]These two would be five. I'm good with doing two and a half. If it'll pull two and a half and lighten that bulb up and not do a big voltage drop, it'll do it'll do the uh it'll do the three and a half. No problem at all. Let's go ahead and get this hooked up because this is really once you know that, right? Once you know what you need to have here now I can just go have this flip on the one bulb. Hook it up. Let's do it.

[00:12:20]Love that magnet.

[00:12:23]I'm going to disconnect this. We're going to take the What we're going to do is take the O2 sensor and disconnect it.

[00:12:30]This is going to be our O2 sensor heater now. Okay. We're taking the O2 sensor offline and we're making this and this is our load. Now, this is going to be our O2 sensor heater. Let's hook it up.

[00:12:44]All right, we're connected in to the O2 sensor heater circuit. We've got our meter hooked in.

[00:12:51]This is why I love having these kind of a connections here on the load box. Now I've got my meter on the same circuits, power and ground that are on the car, and I'm going to be able to check the voltage at at that load box under load.

[00:13:08]If I've got some crazy low number, if it's like the voltage is not not good, then we know there's probably a ground problem or a power problem. Now, we know that there's not going to be because we already see that the ground is good, but potentially the power could be an issue.

[00:13:24]Let's find out. Let's go back over.

[00:13:28]There is no other way, just so you know, to test this. You're gonna have to have a scanner that can do birectional controls. A lot of scanners have birectional controls. And all you need to do is just go in and get the O2 sensor on. Let's turn it on.

[00:13:45]It's activating. Look at our bulb.

[00:13:49]Our bulb is lit up. We do have about a threevolt voltage drop, right? I'm not really concerned about that. I'm I'm okay with that just because it is a duty cycle. We're going to have something a little different. If it was just on, it would be different. You can't just turn it on. But we can see that it can light that bulb. No issue whatsoever. And our voltage drop is good. All right, turn it off.

[00:14:18]Let's do this. Let's go back into it.

[00:14:22]I want to show you guys something. I'm going to go to 5% duty cycle now. Here's 5% duty cycle. It's dimmer. Okay. And look at our voltage drop was way lower.

[00:14:34]Okay? Because now our on time is different. If we go ahead and grab that, you can see that on the scope our yellow is pulling all the way to ground. Now got a nice square wave pulling all the way to ground. All right, let's turn it off.

[00:14:53]There we go. Using ju I get it. Got a load box. We got a meter and we got a scanner. But you don't need a scope, right?

[00:15:04]>> That's I mean that's just stuff you got to have.

[00:15:05]>> You're going to have to have some tools.

[00:15:07]One more final test before we condemn it. Let's test. We know the resistance of a good one. We know that it is 3.5 ohms of resistance. We can easily test the resistance of this one. Now, all we need for that is a meter. And if you get lucky and you just have an open one or you have something that's way out of whack, yeah, you could potentially do this with a meter.

[00:15:29]But again, before I would want to put a sensor in it, I would want to know that we can do everything up to the connector. So, if we're going to go in here, we're going to take the same two circuits, our heater circuits. I've got my meter on resistance now.

[00:15:45]All right. And there we are in it. And look at there. The O2 sensor heater circuit inside of this O2 sensor is completely open. It It should have some resistance there. It's completely open.

[00:15:55]So, we know now that that sensor is no good. Absolutely. There's not a question about it. Yeah, we might have two codes.

[00:16:02]We don't know about the other sensor on the other side, but we know this one's no good for sure. Let's go ahead and get a new O2 sensor in it. And let's go ahead and clear the codes, cycle the key, and see if this code goes away.

[00:16:15]That code will still be there because we're not doing anything with that side yet. But let's see if this one goes away.

[00:16:23]It is pretty rusty. It's tight in there.

[00:16:28]I'm going to use this little nifty tool here and hopefully it'll break it loose.

[00:16:41]Yeah, baby. Oh, yeah. I know. Everybody up north like Okay, dude. Had to break out that thing, huh?

[00:16:53]All right. One sensor.

[00:17:01]All right.

[00:17:05]New sensor is in it. I'm going to leave the scope hooked up because I want to get a good pattern. We'll go ahead and start the scope.

[00:17:13]And let's go back into this. We're not clearing the codes just yet. Let me go back over 25%.

[00:17:19]All right, there it is with the new sensor in it.

[00:17:24]And we can clearly see it now pulls all the way to ground.

[00:17:32]Nice duty cycle. All the way to ground.

[00:17:34]Perfect.

[00:17:36]Now, let's get our stuff out of here.

[00:17:38]Let's lower the car down. Cycle the key.

[00:17:43]Make sure the code doesn't come back.

[00:17:44]Let's go back in to the codes.

[00:17:49]You can see they're both still there.

[00:17:50]Let's erase them.

[00:17:53]The key is on right now. We have not cycled the key at all. All right. We're going to read the codes. Should be nothing comes back. All right. Now, let's go cycle the key.

[00:18:04]And what it's going to do, actually would be really interesting. If you've got a scope and you want to learn about this kind of stuff, have the scope running right now. We have the scope running right now. What it's going to do is it's going to cycle that that heater circuit. You're going to see something happen on the scope as we cycle the key off to on. Let's go ahead cycle the key on.

[00:18:27]There we go. It's cycled.

[00:18:29]That's the computer testing that circuit what it's doing. Hopefully, it liked what it saw. Let's go ahead and read the codes. We should just get the one side now. There we go. Only one we got left is this one. We told you guys we were going to see. Does it need both of them or could there something else be wrong with this? Can't assume. We got to test it. Cast don't guess. Let's go ahead and get to this one.

[00:18:58]a little more difficult to get to.

[00:19:00]There we go. All right.

[00:19:04]And let's go ahead and get We're not going to do it with the scope on this one.

[00:19:12]We're just going to do the load box, the meter, and the we will do the resistance of the actual O2 sensor heater also.

[00:19:26]There we go. All right, we've got Make sure you got your switches in the right spot. Got our meter hooked up.

[00:19:36]We're going to go back into our active test.

[00:19:43]This time we're going to go to bank two, sensor two.

[00:19:51]Let's go ahead and do our 25%.

[00:19:53]There we go. Lit up. And there's our voltage drop. Just about exactly the same as the other one was. All right, we're good there. Got some dirt. You know, dirt's good for you. Got some uh B12 in it when you're working on on cars. Do our resistance test.

[00:20:17]Don't need that one. We need these two.

[00:20:25]So once we do the one side, pretty simple to do this side pretty fast in here. And the hardest part is really finding out what wires are what and that kind of stuff. So here's our resistance.

[00:20:37]What do we got on this one? This one's got 533,000 kiloohms. Make sure you're reading this correctly when you're looking at your meter. That's a lot. What should we be at? 3 and 12 ohms. Bad two. Not open.

[00:20:51]not open. So you can see there's a reading on this one, right? The other one was easy. It was open. This one I had to look at that for a second. Hey, but I will tell you right now, if you don't look at that little symbol done over here, you will get caught at times.

[00:21:04]Make sure you're you're knowing your equipment. So now what we got to do is get an O2 sensor on this side.

[00:21:10]Unfortunately, the O2 sensor is not available in town for some reason on a 2006 Dodge Durango. There must be a gazine of these things running around.

[00:21:17]No parts available in town for this side. We're going to wait for it. But we knew 100% this gonna fix the vehicle.

[00:21:23]We're going to put this O2 sensor in it.

[00:21:25]Car is going to be good to go. No codes are going to be in it. It's going to be fixed. All right, guys. Hopefully that helps you doing these tests, learning how to test, not guess, using some basic Ohm's law, right? It doesn't have to be crazy. Just basic law so that you know how to use your equipment right, so that you can do the test procedure properly and get the answer quick. In this case, yeah, I love to have the scope because I can see it, but you didn't have to have it. Loadbox meter scanner. I know, load box meter scanner. I hope you like it, guys. If you did, you know what to do.

[00:22:00]Jump down there. Hit that subscribe button. Hit that bell notification so you know when we drop a video. Give us a thumbs up. Leave a comment down below.

[00:22:06]Do you know Ohms law? Have you used it?

[00:22:08]Or is this the first time you've seen it? I'd love to know that. Appreciate you watching. We'll see you in the next one.