Error Code P0420
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Senior User
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From: Indianapolis, IN
Error Code P0420
I was driving along today and my Check Engine light came on. I stopped at the nearest Advance Auto to have them pull the code and it came up with the P0420, Catalyst Efficiency Below Threshold (Bank 1). I asked what could cause this and they mentioned that the fuel that was put in could be causing it. They didn't mention any other possible causes. Any others? I'm thinking it could be the fuel because the last gas station that I stopped at and filled up at is one that I never go to, and maybe just got a bad batch of fuel.
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it could be bad gas, but could be a failing cat too. run it low on gas, fill up where you normally do. disconnect the battery cables when you get home, reconnect after 30 seconds to clear the code. if it comes back your cat is failing... its up to you what you want to do, if you have under 80K on it the part is covered but the labor is not.
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Joined: Apr 2007
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I am a technician and I'll tell you the only 2 things I have seen cause a P0420 is abad cat or a bad O2 sensor. The O2 sensor can trick the computer into thinking the cat is not working, but 9 out of 10 times it is the cat.
Brad
Brad
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From: Indianapolis, IN
Great. That's all I need is to have to replace the cat. I'll go through this tank of gas, go to my usual fill up station and have the code reset, see if it comes back. I'm hoping it's just a bad batch of fuel.
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Postmaster
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From: Broken Arrow, OK
It's the cat. Both O2 sensors on that bank have to be working properly for the PCM to recognize that the cat isn't working.
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Senior User
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From: Indianapolis, IN
On general how much is a new cat installed? And while it's being replaced would it benefit me to have high flow cats installed? But COULD it still possibly be the gas that was put in? I'm still holding out hope that it could be the gas.
Post Fiend
Joined: Feb 2000
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From: Kansas
Depends on which side it is. If you go factory it is going to costs some bucks. There is an aftermarket source for the cat assembly. It is considerably cheaper but I haven't heard any reviews of it. Your cats are already high flow.
As far as having them installed it's a pretty straightforward job. Might as well change out the O2 sensors while doing it. I'm looking at doing a manifold back system before too long and that is what I'll do.
As far as having them installed it's a pretty straightforward job. Might as well change out the O2 sensors while doing it. I'm looking at doing a manifold back system before too long and that is what I'll do.
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From: Indianapolis, IN
I know for a fact I won't take it to Ford to have them do it. If any it's something straight forward and not too difficult I'll go buy the cat and my uncle and I can do it. Now, if I'm replacing one already would it be beneficial to go ahead and replace the other as well? Also by going aftermarket will it help the sound of my exhaust any? If I'm replacing them might as well put in one(s) that'll help and work great instead of putting new ones in just to replace them again with better ones within a year.
Post Fiend
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From: Kansas
Originally Posted by Munky
Now, if I'm replacing one already would it be beneficial to go ahead and replace the other as well? I have one that has a hole in it. I'm at 108K and will replace the other side when I do it.Also by going aftermarket will it help the sound of my exhaust any? No. If I'm replacing them might as well put in one(s) that'll help and work great instead of putting new ones in just to replace them again with better ones within a year.
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From: Indianapolis, IN
Alrighty, just thought I would ask about the exhaust sound just in case. I've been driving the truck the past few days with this problem and it hasn't really effected anything and it's not a pain in the rear to drive. Would it hurt it much to continue driving it like this until I'm able to get it tested to make sure it's the cat? I do plan on taking a trip to Kansas over memorial weekend to pick up my Harley, would that not be a good idea with this problem or would it be okay? I do plan on getting it fixed, whatever the problem, just can't afford it at this particular moment.
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From: Broken Arrow, OK
Originally Posted by Munky
But COULD it still possibly be the gas that was put in? I'm still holding out hope that it could be the gas.
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From: Indianapolis, IN
Alright, bad gas was something that both Advance Auto and Auto Zone both told me that it could be. Is there a way other than taking the truck to the dealership that I can tell if it's the cat, something I can do on my own at home?