So, I’ve seen this code before and I used to think most of the time you would have to replace the catalytic converter but what I have found out is that a lot of the time that isn’t the case.
What is Engine Trouble Code P0420 and P0430?
When your vehicle comes up with the diagnostic trouble code P0420 and P0430, it will say that the catalyst system efficiency below threshold. P0420 is bank 1 and P0430 is bank 2. The main job of the catalytic converter is to burn up fuel coming though the exhaust so that it improves emissions and produces less harmful fumes coming out the tail pipe. The downstream oxygen or 02 sensors (the sensors past the catalytic converter) are suppose to read what comes out of the catalytic converter to make sure that it is doing it’s job. If the oxygen sensor picks up anything other than normal flow, it’s going to pop this code.
Possible Causes of P0420 and P0430
- Bad / clogged Catalytic Converter
- Bad Oxygen Sensor
- Exhaust Leak
- High Fuel Pressure
- Using the Wrong Fuel
- Outdated PCM Software
These are the most common causes of P0420 and P0430, there are a few others but these are the most common that should be ruled out first.
How to Fix it P0420 / P0430 and What to Look at First
For this fix we are going to focus solely on the catalytic converter because 90% of the time this is the cause. The first and easiest thing you can do is to feel the output of the exhaust at the tailpipe and determine if you are getting enough exhaust coming out. If the catalytic converter is clogged on bank 1, you’ll notice that bank 2 or the other side is putting out more exhaust. The second thing you can do if you can get underneath the car is to use a temperature gun and check the temperatures at the front of the catalytic converter and the back. Normally, the back of the catalytic converter will be hotter than the front. If the front has a higher temperature than the back, you have a restriction. You can get a temperature gun for a good price on amazon, here’s a good one:
One thing that I just recently learned is that these codes (P0420 & P0430) can pop when the catalytic converter is working less than 92% (or close to it). So, even though the code has appeared, doesn’t mean the catalytic converter is bad. If you live up north and have to get state inspections, it will not pass with this code present. So, lets say you can’t get underneath the car to check the temps before and after the catalytic converter, we have one more thing we can do which is commonly overlooked. There is a Product called Cataclean, it is very simple to use and can actually clean out the catalytic converter and clear the code. It will clean up carbon build up in the exhaust but it will also clean the fuel system and supposedly clean up the cylinder heads. I have personally tested this product and can confirm that it does work and will help clean out the catalytic converter. When you use it, make sure you have half a tank of gas or less (don’t put it in with a full tank of gas). You’ll have to run the vehicle for about 150 miles to let it do its job. Here’s a link to Cataclean on Amazon:
Honestly, I didn’t believe this stuff would work until I had a friend pop this code on his older Honda. I quoted him a price for a new catalytic converter and if you’ve ever seen the prices for them, they are not cheap. So, I discovered this stuff and told him to put one bottle in at half a tank of gas and run it for 150 miles and once I cleared the code, it never came back on and he also told me that it seems like his mpg had increased. I told him to go ahead and use the 2nd bottle after 2-3 months and he still hasn’t had the code pop back up yet.
Of course, if this code pops up for you, depending on the make and model of the car, it’s not always going to be the correct fix but it’s the cheapest option before taking it to a mechanic or fixing it yourself. if you have ever messed with exhaust, it’s always a pain trying not to break bolts and sometimes the catalytic converters can be in hard places. If you do have this code pop up, give this method a try first and let me know if the comments if it worked for you!
Thank you for taking the time to read this post and if you have any questions or would like to see an article on this blog, you can email me at lubetechcurt@gmail.com.
