Mark: Hi, it's Mark Bossert. I'm here with Bernie Pawlik, Pawlik Automotive in Vancouver, Vancouver's best auto service experience, 25 times the winners of best auto repair in Vancouver. We're talking cars. How are you doing Bernie?
Bernie: Doing very well.
Mark: So today's victim is a 2014 Mercedes, Mercedes and their long names, Mercedes Benz. ML63 AMG. What was going on with this vehicle?
Bernie: Yeah. So this vehicle came to our shop with a check engine light on running fine. That's basically what was happening.
Mark: Check engine light running fine. So where do you start?
Bernie: Start with a scan tool interrogation of the vehicle computer. So we basically plug our diagnostic scan tool in and we found a code for an oxygen sensor. Don't have the code number in front of me, but basically it was the left bank rear oxygen sensor. So there's a code for that. And to proceed with our diagnosis on that particular code and that issue.
Mark: What did you find was wrong?
Bernie: Well, what we found is just over a year ago, we actually replaced this oxygen sensor on this vehicle. And doing a little digging. We noticed when we looked inside the connector of the oxygen sensor that we've replaced a year ago, there's a tiny bit of oil in there. Oxygen sensors last a very long time these days, and there's no reason why this one we changed a year ago shouldn't be in perfectly good shape for the next 10 years.
What was happening is basically oil was getting into the engine wiring harness and working its way down into the oxygen sensor. And that's what had caused this code. So on further exploration, we pulled the plugs off the computer. You could see the connectors. There's two large connectors with many terminals. There was oil in that area too. So oil had infiltrated the engine wiring harness, and that's what had caused this oxygen sensor code.
Mark: So, were there any other issues that were causing the oxygen sensor to fail, and was it failing?
Bernie: Well initially we actually left the oxygen sensor, cleaned the terminals and figured that the thing to do would be to actually deal with where the oil was coming from and work on that. Because otherwise, whatever we do, the oil is going to work its way through the wiring harness more. It's going to get into other sensors, other places into the computer and cause some pretty serious issues.
Mark: So do we have some pictures? Whereabouts on the engine is the oxygen sensor on this vehicle?
Bernie: The oxygen sensor is right at the very bottom. So this is probably about the lowest piece of wiring on the engine wiring harness, which is why the oil has kind of worked its way down into that connector.
But where the oil comes from, which is probably what you're wondering, is it comes from the camshaft sensors. We'll get into some pictures. So there's our beautiful AMG vehicle. Very nice car to drive, by the way, not just from the point of view of the power, but just a really nicely built SUV.
So there is a picture, unfortunately, a little out of focus. This is one of the connectors to the computer. And if the camera had better resolution and unfortunately using a smartphone sometimes just doesn't pick up details as well as we'd like. But this area here, there's oil in this area here on this connector.
And the oil comes from, the camshaft position sensors. And this is the connector here. Again, you can see oiliness on this connector.
Again, oil in this connector. So there's four camshaft position sensors that sit on the valve covers, and these leak oil.
There's another view of the connector here. The other view I was saying was out of focus, that was actually the computer terminals, but this is a connector here. Again, it's a little out of focus in this spot, but you can see an oily film right here. So oil basically works its way from the camshaft sensors through the wiring into this plug. And then it kind of, from there works its way into the rest of the wiring harness. And that had worked its way down into the oxygen sensor wiring.
Mark: So it's just siphoning around through the wiring, basically.
Bernie: Yeah, it just works its way around through the wiring. So eventually it will get into the computer and you know, the oxygen sensor.
This is the oxygen sensor too, by the way. So I don't have a view inside of any oil in there, but it was minimal, but it was enough. Like when you get oil runs down one of these wires, it gets in there and it contaminates. It's like. A heater and all the components of the sensor are very sensitive. So if you get oil inside of it, it just wrecks it. And so that's what happens.
Mark: Yeah. I imagine something that is measuring the amount of oxygen in the air or in the exhaust has gotta be a pretty finely calibrated instrument essentially.
Bernie: It is, absolutely. And you know, it measures it compared to ambient air, so it senses the outside and the inside. So there's a lot going on. And the rear sensors are actually a more, I would say a more crude it's precision, but it's a little cruder than the front sensors. They're called a wide band sensor and they use even more precision measurement to trim the fuel.
The rear sensors are basically just telling the computer, Hey, this is what's coming out of the catalytic converter, and it'll do a little more trimming of the fuel mixture from there as well, but it really monitors the catalytic converter efficiency.
Mark: So you mentioned that you first you tried cleaning the sensor connector and what happened then?
Bernie: Okay. So I'll just go over the whole repair. So there's really, there's really two options at this point. So the camshaft sensors were the cause of the leak. Now, two of them were okay. And two of them were leaking. So replacing the cam position sensors, there's four in total, is the first step in the operation. From there, there's two options. You can basically replace the computer. Replace the engine wiring harness.
As you can imagine a very expensive, hIghly labour intensive operations, or we can clean the wiring harness, clean all the connectors as best we can. And see what happens with no guarantee that it's going to long term work, but at least it'll stop any extra oil flow from getting into the engine by changing the cam sensors and cleaning whatever we can.
So that's the option the customer opted for. We cleaned everything. The check engine light was off. So we left the oxygen sensor there after we cleaned the connectors, figuring it was going to be okay. A couple days later, it came back with the check engine light on. The sensor got wrecked, so we had to replace that as well. So, sensor done. I mean, it's been a few days. We haven't heard back. I'm sure it's going to be fine now. But as I said, you know, we tell people, if you want a guaranteed job, it's a new engine wiring harness, along with a computer and many thousands of dollars. Yeah. Yeah.
Now the sad thing about this vehicle is it's a 2014, so it's nine years old, but it's only got 55, 52,000 kilometres, which is practically brand new.
Mark: Was this issue unique to this AMG engine or is this happened with other vehicles?
Bernie: No, it's actually kind of a common Mercedes issue. We work on a lot of Mercedes, so we don't see it on all of them, but we've seen it on several. And I've seen it all the way back. I can think of like a 230CLK or SLK, CLK, anyways, the four cylinder model with the supercharged engine and, you know, seeing those cam sensors leaking and a similar issue with the oxygen sensor bad and oil going through. So this is an issue that's been going on with Mercedes vehicles for quite a long time.
Now, I don't know if brand new ones have that, but we never know how things have been changed on vehicles, but you know, it's something that's been going on for a couple of decades.
Mark: So would it be a good idea to inspect these cam position sensors on a regular basis as a preventative maintenance kind of?
Bernie: Absolutely. It's a very good idea. It's not very difficult to just pop the wiring connector off. You know, there are many things on cars that are difficult. These are generally pretty accessible and pretty easy to access. So you could pull a wiring connector off and all of them. You see any oil in them, change the sensors and, you know, clean it out before anything worse happens. Definitely be a good preventative operation for sure.
Mark: So once you completed all the repairs, the vehicle was running well?
Bernie: Yeah. It was running well. And I say it ran well beforehand too. The check engine light is off, so we'll hope it stays that way for the customer for a long time. But, I think personally, you know, for the amount of money, I sort of think if it was my own car, you know, it seems we've actually fixed the cam sensors, it would probably be worthwhile if the light comes back on to just clean the harness again and do the sensor. It would almost be possibly more economical to do that a couple of times than to change everything. But it's really a matter of how long it lasts and what happens.
Mark: How reliable other than that, how reliable are these 2014 ML63 AMGs?
Bernie: Yeah, generally they're pretty good. It's a really complicated vehicle. So, you know, there's a lot of fancy fanciness to it but generally a pretty reliable vehicle with a few issues here and there. It's an expensive vehicle to buy and you'll spend a lot more money to do repairs on the vehicle than you would on a lesser model and, you know, on a less fancy vehicle.
So just, you always got to keep that in mind. And of course, do your services and oil changes.
Mark: Just as important on Mercedes as it is on every other vehicle.
Bernie: You know, exactly. It's just as important on them and a lot of European vehicles have a very long oil change interval. They use fancy synthetic oils and they think you can leave everything for way longer. That's the idea, but you can leave your oil service intervals longer than your sort of usual conventional oil, but you don't want to go too long because otherwise it goes bad and causes lots of issues.
Mark: If you're looking for service for your Mercedes Benz in Vancouver, the guys to see are Pawlik Automotive. You can reach them on the website to book at pawlikautomotive.com. There's also hundreds and hundreds of videos. We've been doing this for over 10 years. All makes and models and types of repairs. Guaranteed to put you to sleep. As well you can call at (604) 327-7112 to book your appointment. You have to book ahead. They're always busy. Pawlik Automotive in Vancouver, BC, Canada. Thanks so much for watching and listening. Thanks, Bernie.
Bernie: Thank you, Mark. And thank you for watching.