June 1

Chevy Suburban Oxygen Sensor Replacement

Podcast2018, Chevrolet


Mark: Hi, it's Mark Bossert here, producer of the Pawlik Automotive podcast, here with Mr. Bernie Pawlik. We're talking cars. How you doing, Bernie?

Bernie : Doing very well.

Mark: So, we're talking about a Chevy Suburban, had a oxygen sensor replacement, which is a pretty common issue. What was going on with this large SUV?

Bernie: Well the check engine light was on. We scanned the vehicle computer. There was two codes for heated oxygen sensor circuits, for the front two oxygen sensors.

Mark: So, what does an oxygen sensor do? I know we've talked about it with other vehicles. How does it work?

Bernie: So there's a couple of functions for oxygen sensors. This vehicle is a 2001. It's a little older, but the technology is the same, even right up to brand new. Essentially, what the oxygen sensor does, is it reads the oxygen content in the exhaust and sends a signal to the vehicle computer. With that it can do a couple of things. There are your front oxygen sensors. These are located in front of the catalytic converters, right at the downstream of the engine. It'll read, is the engine running rich or lean. It sends a signal to the computer, it's rich. The computer leans out the fuel mixture, gets a signal it's lean, it richens it up and this cycle happens very quickly, like imperceptible. It richens and leans the mixture, so it makes quick readjustments for optimum fuel mixture, based on what the computer wants. The rear oxygen sensors are located downstream of the catalytic converters. What they do, is they monitor the efficiency of the catalytic converter, to make sure it's working. Essentially, modern vehicles ... used to be in Vancouver, we'd have air care and a lot of the testing was done with a dynamometer, with gas analyzers. You don't need to do that with any vehicles that are built after 1996. They're all self-diagnosing vehicles, because it has an oxygen sensor downstream of the catalytic converter. That's essentially what an oxygen sensor is, and how it works is it basically generates a voltage based on how much oxygen is in the exhaust system, so basically kind of a self-generating piece.

Mark: So mainly, let's just dig into a couple things. So rich and lean is referring to how much fuel there is in the air/fuel mixture?

Bernie: That's exactly what it is. There's a certain ideal ratio, about 14.7 to 1. It depends on what condition. If you're stomping on the throttle, and you want to go really fast, you want a richer mixture. If you're coasting down a hill, it goes leaner, but the vehicle computer's programmed for whatever that optimum mixture is. So yeah, it's a air to fuel ratio.

Mark: When you were mentioning downstream, you're talking about what's coming out of the exhaust, going out the tailpipe.

Bernie: Exactly, yeah. Downstream is like from the engine. If you can imagine, the exhaust is like a river. It's going down ... I don't know, river, downhill, exhaust, the stream exhaust goes out of the engine, goes back to the tailpipe and out into the air.

Mark: All this is an aid of basically the vehicle running good, but also it's an important factor in removing pollutants from the exhaust stream. Is that right?

Bernie: Absolutely. Absolutely. In the olden days, when cars had carburetor and they just kind of calibrated everything as best they could, there was no oxygen. It actually went to a feedback carburetor, which actually had an oxygen sensor and it would actually readjust the carburetor, but it was very crude. There's only a certain, limited amount of adjustment you can make on a carburetor versus a fuel injection system, which is why everything's fuel injected. So much more control.

Mark: Are there any other types of sensors in the exhaust stream that are part of this process of making sure the engine's running right?

Bernie: On a gasoline engine, there isn't, but we say oxygen sensor, there's actually a lot of vehicles use what's called an air/fuel ratio sensor. This Suburban is kind of older. It's a 2001. It uses an oxygen sensor in the front, but a lot of newer vehicles will use what's called air/fuel ratio sensor. It performs the same basic function, but it works differently. It's able to make adjustments to the fuel system much quicker and over a wider range. It's often called a wide band oxygen sensor as well. It works a little differently, but essentially the same function. They usually cost a lot more money than an oxygen sensor. Other than that, that's the only two ways they do it.

Mark: How often to oxygen sensors wear out?

Bernie: Well, this Suburban that's actually got over 300,000 kilometres, and the sensors have finally worn out, but they'll typically last 100,000 to 200,000 kilometres. Just a little history, in the olden days the oxygen sensor used to be a single wire, and it would self-generate its own electricity. Electric voltage signal, usually from zero to one volts, based on how much oxygen was in the exhaust. It would have to warm up and be at a certain temperature. It would often take a few minutes of engine running to get that sensor warmed up. In the meantime, the fuel system is what's open looped. It's pumping a lot of pollution, so what they did is they created a heated oxygen sensor, which everything has been for a long time. Heated oxygen sensors not only work almost immediately, like within a few seconds, but they also last a lot longer, so a single oxygen sensor in the past would never have lasted as long as the ones in this Suburban.

Mark: How would I know if the oxygen sensor were worn out on my vehicle?

Bernie: Normally, it's a Check Engine light issue. The Check Engine light comes on, and through diagnosis, we find the oxygen sensor's worn out. Occasionally, you'll have a physical problem, like the sensor will actually break apart. Maybe they'll be an exhaust leak. Not very common. Usually, 99% of the time, it'll be through the Check Engine light deal and diagnosis, so that you'll know that sensor's worn out.

Mark: Is this a large job, to replace these sensors?

Bernie: Well, it can and can't be. The Suburban was absolutely miraculous and beautiful. Oxygen sensors have bolted in the exhaust, and as you can imagine, there's a lot of heat that takes place. There's a lot of rust that occurs. Often, when we go to remove them, they won't come out very easily, but when you install a new oxygen sensor, you also put some Never-Seez, which is a compound that supposed to prevent the threads, as the name implies, never seize. They obviously did well with this vehicle, because all four oxygen sensors requires a little crack with a wrench, and I was able to spin them all out by hand, which is kind of miraculous. We have a lot of vehicles, where you go to undo it, and it takes the threads out of the exhaust system, involves a lot of extra repair.

Mark: So, what do you do in that case? Are you welding in a new piece, into the exhaust system? Can you even do that?

Bernie: Yeah, you can. Actually, you can cut the old piece off. It's called an 02 sensor bung, and we can just weld another one in and away it goes. It's a bit of extra work. Now, depending on where it's located, it might actually be a lot of extra work, because some oxygen sensors are buried way in the engine compartment. There's no room to move, and so it can be a lot of work.

Mark: And this Suburban, as you mentioned, is getting on a bit in age. Is it still a worthwhile vehicle to keep on the road?

Bernie: Absolutely. Again, it's all about maintenance, but like a 2001 Suburban, it's kind of when they changed this newer style of vehicle. I think GM has done a great job with these Suburbans and these pickup trucks of this era. They are far more reliable than they used to be in the past. Brakes last a long time. The engines are really good. Overall, a really good vehicle. I recommend them. Just keep them going. Just do the maintenance as things need to be done and the repairs. It's a good vehicle, last a long time. I realize we've been talking a lot. We haven't shared any pictures, so let's go to look at a couple of pictures.

These are the four oxygen sensors that were removed from the vehicle. The front and rear are actually different sensors, but the function they perform is the same. There's some calibration, there's something that's a little different between that two of them. So these are the four sensors that have been removed. You can see that these are plugs have been connected into the wiring harness. This is the end that screws into the exhaust system, over here. It looks kind of crusty and old, because it is. The next picture we'll go to, this is a close-up view of the wiring connectors. I mentioned, in the olden days, there was just a single wire oxygen sensor. Usually, on the GM it was a purple coloured wire. One of these wires is a ground wire, to make sure there's good ground to the sensor. Then the other two wires are for the heating circuit. So the heating circuit's monitored by the vehicle computer, and as I mentioned, there was a trouble code for this. If something goes wrong with the heating circuit, which is a frequent problem in these sensors, it'll set off a trouble code, saying the heater's not working. Finally, a view of a 2001 Suburban. There we go. Still in good shape after all these years.

Mark: Awesome. So there you go. If you're looking for service for your Suburban, or for an oxygen sensor replacement in Vancouver, the guys to see are Pawlik Automotive. You can reach them at 604-327-7112. Or check out their website, pawlikautomotive.com. Or our new podcast and channel on YouTube. Check us out. There's hundreds of videos on there. Thanks Bernie.

Bernie: Thanks Mark.

About the author 

Bernie Pawlik

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