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Discussion Starter · #1 ·
Hey,
2008 Accord sedan 4cyl
I was driving to work when my CEL came on, the car had no issues previously, I know it’s something to do with the catalytic converter. The only thing right now is my oil life is at 15% (I kept putting it aside, my fault) I won’t use it until I do the oil change in 2 days. Could that be a reason why? I bought the car with a muffler delete around 5 years ago but was good shape overall. Currently has 155K miles. I could replace the converter but that will be a matter of time until it goes bad again. I’ve been looking at other threads but don’t know of a good way to approach the problem. Any help is useful🙏🏼
 

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2010 Honda Accord (LX)
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Has it been burning oil?
 

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Discussion Starter · #3 · (Edited)
I hadn’t had an issue with it burning oil, however I do recall it leaking a very small amount of oil. Does the P0420 code mean that the catalytic converter is done for and will NEED replacement or can it be fixed with some steps?

If the oil is dirty, and I do the oil change, would that maybe get rid of the CEL? On Saturday I will replace the pcv valve and the full oil change. I’m seeing that many are recommending to start with the O2 sensor. But I also saw to check for a vacuum leak which sometimes sets the light on, but how do I do that? Lastly, I have a scanning tool, what should I be checking for on the freeze frame? Thank you for your response.
 

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P0420 has nothing to do with burning oil. It means one of your O2 sensors is reporting that the catalytic converter (cat) isn't doing its job properly. Being that the cat is a catalyst and not a wear item, the more likely issue is the O2 sensor is toast.

First replace the downstream O2 sensor and reset the code. If this doesn't fix the problem replace the upstream sensor. I'd wager you no longer have the CEL after this.
 

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Discussion Starter · #5 ·
Alright man, lifesaver. I needed some guidance with this. Would an autozone sensor be good enough for this? So the code doesn’t necessarily mean the cat is finished and MUST be replaced?

Lastly, if the O2 sensor is what’s bad, why did it go out? (Or usually go out) Mainly just to prevent it from happening again
 

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Turbo lag
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Use the Denso sensor, find the Denso part number and not the Honda part number. Exact same part, but half the price.

Yes, O2 sensor can just stop working sometimes. Mine did, two different times. The original sensor lasted 150k miles (it didn't break, I prematurely replaced it for better readings), the 2nd and 3rd lasted only 5k miles, and this 4th one still works after 15K miles.
 

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Yea I modded my car again
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If you wanna know if ur cat is mangled you need to simply remove the top (upstream) o2 sensor and then look down that hole and inspect the cat cells. If they don't look nice then that's ur problem. The lower (downstream) o2 sensor is the one that reads cat efficiency and is what triggers the code. However, lets say the cat is damaged and you replace it and everything seems fine again. That doesn't mean the issue is fixed for sure. The car may be doing something that is damaging the cat converter. Running rich or burning oil are the two main culprits for cat failure.

I would say the odds are more likely the cat is bad then the o2 sensor is giving you a false code.

I just recently got a p420 code (it would come and I would clear it and I wouldn't see it for months). Well I bought an Endoscope and voila not only is my front cat destroyed but the rear cat is also destroyed. But I had weird misfire issues for 3 years that would come and go and I am sure that's what pooched them.

In a perfect world a cat converter should be good forever. I have had family vehicles that were 20 years old and never touched the cats.
 
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