P0420 Code: What Your Mechanic Might Not Be Telling You

Transcript In this video, I'm going to explain the P0420 code, which is an OBD2 code, which relates to the catalytic converter. I'm going to do it completely in layman's terms. So, if you don't understand mechanics, that's perfectly fine, but you will understand the importance of this code. And if you need to do something that might cost you a couple thousand dollar or you might be able to do something might cost you a couple hundred. But in the end, you will understand this code so well that you will be able to talk educationally to a mechanic about the situation. You will be educated enough that the mechanic can't give you false information and that you will know enough that if you decided to possibly fix it yourself, you would have a strong background on how to fix this particular code or at least troubleshoot it to the point where you can make a decision if you want to spend a little bit of money and have the problem go away or a lot of money. This video is going to be extremely helpful. it. By the end of this video, you will know all you need to know about a P0420 code. Let's get started. Now, let's make believe that you have a check engine light on. You either took your car to an AutoZone or O'Reilly's and got a free code reading or you had your own code reader and you got the P0420 code. What does that mean? it means the catalytic converter is not working efficiently and there could be a problem either with the two sensors that are connected to it or the actual catalytic converter itself. Now there's a sensor going into the catalytic converter that reads the pressure or the airflow going into it or the gases I should say. And there's a sensor on the outside of the catalytic converter on the exhaust part where the exhaust is coming out. And these two sensors read what's going on from point A to point B. So that's where we're at. Now let's move on. Since you understand, I hope how the catalytic converter works and what it does, we'll move to the next part. So the way it actually works is it's actually the first sensor is reading a voltage and if that voltage is high enough when the gas has come into it I believe it's nitric oxide and another gas it reads those gases and it passes through the catalytic converter which is loaded with precious metals by the way that's why they're so expensive and then it comes through the outside sensor which also reads the voltage and gives us where it's at, if it's working properly or not working properly. So you understand how it works. You can see that there's gas passing through the catalytic converter. Its job is to clean that gas and it's based on voltage and it's based on precious metals that are in the catalytic converter. And by the way, those precious metals are very expensive. And that's why catalytic converters, if you have to replace them, cost around $2,000. And some cars have two catalytic converters. They have a bank one and a bank two. So, they're on either side of the engine. When a catalytic converter gets clogged up or doesn't work properly, it can create problems with engine horsepower or actually the uh the engine's power to accelerate. So, when the catalytic converter is working properly, what's happening is the voltage is steady, okay, on the first O2 sensor. And if that voltage is steady, that means that it's cleaning the gases properly. So why would you get a P0420 code? It's when the downstream sensor, the one on the opposite side, the exhaust side of the catalytic converter, starts to um read a high voltage or an equal mirrors the voltage of the incoming sensor, which means that the catalytic converter is not purifying the air like it's supposed to. The good news is that, okay, when you get a P0420 reading, it doesn't always mean that the catalytic converter is not working properly. Sometimes the O2 sensors are bad. They're not functioning properly, and sometimes that's all the repair requires. So, let's explore a little further and see where it brings us. Now, I want to give you a couple of things that it could be outside of it being the catalytic converter. If the car is misfiring, in other words, you hear that it's it's just not firing properly, it's running rough, that can cause the fuel to not burn properly and give us a false reading in the catalytic converter. That's number one. And number two is, like I said, the O2 sensor could be giving us a false reading cuz it went bad. In essence, what's going on is there's nothing wrong with the catalytic converter. It's the O2 sensor that's sending the wrong message to the computer and the computer's reporting the P 0420. Does that make sense? And the third reason that we may get a problem with that P 0420 code is if there's an exhaust leak before it reaches the O2 sensor, the first one, the one coming into the catalytic converter. And if we have an exhaust leak, it could be pulling air into it and pushing it through and giving a totally false reading on the way out. And therefore, it could just be an exhaust leak as opposed to a bad catalytic converter. And that's the third reason. Let's do one more and we'll close this up. And finally, the last one would be contamination. If oil leaks onto the catalytic converter or possibly antifreeze leaks onto the catalytic converter, these things can cause the catalytic converter to actually fail or not produce the the proper output. So, there we have it. Those are the four reasons that it could be something other than the $2,000 catalytic converter. So, how would you possibly know if there's a problem with the catalytic converter if you didn't have the check engine light? First, of course, is the check engine light. The second thing would be a rotten egg smell coming out of the exhaust. And that's because the exhaust is not being purified like it's supposed to. And the third thing would be a loss of engine power, maybe passing power. you notice that when you're trying to pass somebody, the car is not doing its job with acceleration. That would also indicate that the uh catalytic converter is possibly clogged a little bit. So, how do we verify this? And should we buy a catalytic converter right away? Absolutely not. First, we need to check for other codes. A P 0300 series code like P 03000123, those codes could mean that the engine has a misfire. is it has a if it does have a misfire, you need to correct that problem first. The other possibility is we need to look for exhaust leaks. If we have an exhaust leak somewhere, and you could probably hear that exhaust leak cuz it's typically before the uh the muffler itself, then you know that that needs to be fixed first. So, always check for the root cause first and fix those things first before you move on to spending big money on a catalytic converter. So P420 is not a death sentence to your wallet, but it is an indication that there's some problems. There's there's some thing that other things that need to be looked at. So I suggest if you're not mechanical yourself, then have a qualified mechanic go through and diagnose the problem correctly and just make sure that he's going to check for the oil leak. He's going to check the O2 sensors first. He's going to check the most inexpensive things first. maybe a misfire, maybe a bad spark plugs, stuff like that. He's going to go through that first before you spend the big money on a catalytic converter. I hope this helps you understand how the catalytic converter works, helps you to diagnose the problem, whether it be the actual catalytic converter or some other sensor or a misfire or an exhaust leak. And uh this will probably save you a whole bunch of money if it turns out not to be the catalytic converter. And you can talk educationally with your mechanic with this information if you want to turn it over to a mechanic to let him do it. If you want to see exactly how to test an O2 sensor, just put it in the comments and I will create a video on how to test an O2 sensor and then you can do that diagnostics yourself as well. Anyway, I hope you enjoyed the video. So, I hope you learned something from this and uh if you want, you can it would be wonderful if you could give me a like uh subscribe cuz there'll be on ongoing videos. We're planning on creating over 200 videos to explain the different problems used cars might present or have. And we're going to cover most of the uh common P 0 codes or the OBD2 codes that show up when you're looking to buy a car or on your own personal car. That check engine light is very important. It gives you information that you really need to look at before things get worse. It's telling you that you might have a problem. It's not always expensive. It could be a very economical problem, but if you wait sometimes, it could become a very expensive problem. Heed my warnings. I think that everybody should have an OBD2 code scanner in their car. It's a very simple test. You literally plug it in under the dash. There's no way to plug it in wrong. And you read the codes. There's a there's a button on there. You click and you literally press read codes and it does everything for you. It'll tell you what's wrong. It'll tell you, it'll give you what the possibilities are. And then if you put it, if you run it through the Car Value Scout app, it'll tell you the actual cost to have those codes repaired. It's extremely helpful. And I mean, your car is your second largest purchase outside of your house typically for most everyone. Kind of great information to have. Thanks for watching and see you in the next