(08-30-2024, 11:58 AM)Nicko Wrote: I’ve got an error code P0420 showing up on my 2014 Corolla’s dash, and I’m not entirely sure what it means or what’s causing it. From what I’ve gathered, it seems to be related to the catalytic converter or the oxygen sensors, but I’m not really sure how to diagnose it properly or what the next steps should be.
Has anyone else run into this P0420 code with their Corolla? If so, what ended up being the issue—was it the catalytic converter, an oxygen sensor, or something else entirely? And more importantly, how did you go about fixing it? Did you have to replace parts, or was there a simpler solution like cleaning or reprogramming something?
Hey! The P0420 code on your 2014 Corolla is pretty common, and you’re right—it’s usually related to the catalytic converter or the oxygen sensors. I’ve had this code pop up before, and in my case, it turned out to be a worn-out catalytic converter. However, before jumping to any conclusions, it’s a good idea to check the oxygen sensors first, especially the one downstream of the catalytic converter (the one after the cat). These sensors can sometimes give false readings if they’re faulty, which might trigger the P0420 code.
Here’s what I’d suggest: start by inspecting the oxygen sensors. If you have an OBD-II scanner, you can check the live data to see how they’re performing. If the sensors seem fine, then it’s more likely the catalytic converter itself that’s causing the issue. Unfortunately, if the cat is the problem, you’ll probably need to replace it, which isn’t cheap, but it’s essential for keeping the emissions in check.
Some people have tried using fuel additives that claim to clean the catalytic converter, but that’s more of a temporary fix if it works at all. If you’re comfortable with DIY, you could try replacing the sensors yourself first, which might save you some money if they turn out to be the issue. Otherwise, it’s probably best to get a mechanic’s opinion before replacing the cat. Hope that helps! Let me know if you have any other questions.
(08-30-2024, 11:58 AM)Nicko Wrote: I’ve got an error code P0420 showing up on my 2014 Corolla’s dash, and I’m not entirely sure what it means or what’s causing it. From what I’ve gathered, it seems to be related to the catalytic converter or the oxygen sensors, but I’m not really sure how to diagnose it properly or what the next steps should be.
Has anyone else run into this P0420 code with their Corolla? If so, what ended up being the issue—was it the catalytic converter, an oxygen sensor, or something else entirely? And more importantly, how did you go about fixing it? Did you have to replace parts, or was there a simpler solution like cleaning or reprogramming something?
Hey, I’ve dealt with that pesky P0420 code on my 2014 Corolla too, so I can totally relate. That code is indeed tied to the catalytic converter's efficiency, but it doesn’t automatically mean the cat is bad—it could be an oxygen sensor acting up as well.
In my case, I started by checking the oxygen sensors because they’re easier and cheaper to replace. You can use an OBD-II scanner to look at the live data from the sensors. If the upstream and downstream sensors show similar readings, it might point to a failing catalytic converter. However, if the upstream sensor is reading normally and the downstream sensor is out of whack, then the sensor might be the problem.
For me, it turned out to be a bad downstream O2 sensor. I replaced it myself, which wasn’t too hard—just make sure you have the right tools and a bit of patience. After replacing the sensor, I cleared the code, and it hasn’t come back since.
If it’s the catalytic converter that’s causing the issue, unfortunately, you might need to replace it. Some people try using fuel additives that claim to clean the catalytic converter, but I haven’t heard of consistent success with that method. Also, if the problem is more severe, like a clogged or damaged cat, those additives probably won’t help much.
So, I’d recommend starting with the oxygen sensors, and if those seem fine, then you might need to look at replacing the catalytic converter. Hopefully, it’s just a sensor and not something more expensive. Good luck, and feel free to ask if you need more help!
