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2012 Honda Accord SE 2.4L 4Cyl Automatic
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Discussion Starter · #1 ·
Got this code on my son’s 2012 Accord SE with 228,400 miles; Catalyst System Efficiency Below Threshold Bank 1. Vehicle is running fine; no hesitation, shaking or other crazy signs of any issue going on. Trying to figure out if it’s just the O2 sensor or the Catalytic Converter. The first being the easiest and cheapest, was thinking of just going ahead and replacing that and see if code goes away. But before even doing that I wanted to get others’ opinion whom maybe had this code pop up before.
 

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Turbo lag
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Is the car burning oil?
 
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2012 Honda Accord (EX-L V6)
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At your mileage it could easily be either, especially if you're burning oil as is somewhat common with this era of K24, but I'd start with the O2 sensors. If you replace the cat later, you'll want fresh O2 sensors on it anyway so might as well try the fresh sensors first.
 

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Discussion Starter · #4 ·
Is the car burning oil?
Not burning oil. Oil levels check have stayed consistent. Bought the car back in late July with 226k miles for my son as his first car to get to and from college/work. Did a bunch of regular maintenance to get it up to date on the service (coolant flush, power steering flush, oil change, new air filter, spark plugs, etc). Had an oil analysis done by Blackstone Labs and report came back as great. No issues with contamination or anything. So car is running great. No loss of power or hesitation.
 

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It's probably just a bad O2 sensor then.
 

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Discussion Starter · #6 ·
At your mileage it could easily be either, especially if you're burning oil as is somewhat common with this era of K24, but I'd start with the O2 sensors. If you replace the cat later, you'll want fresh O2 sensors on it anyway so might as well try the fresh sensors first.
Thanks for the reply. Looked them up and for both O2 its around $140, both Denso, not bad. And I would replace myself. If it’s the Cats, then looking at around $400 for both. Looks like bolt on so I should be able to also do myself.
 

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I hope that’s the case. Isn’t there a code that’s more specific to the actual O2 sensor(s) being the issue?
Not necessarily. Failing O2 sensors can just throw a P0420 code, especially the downstream sensor since that's what monitors the cat health.
 
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Got this code on my son’s 2012 Accord SE with 228,400 miles; Catalyst System Efficiency Below Threshold Bank 1. Vehicle is running fine; no hesitation, shaking or other crazy signs of any issue going on. Trying to figure out if it’s just the O2 sensor or the Catalytic Converter. The first being the easiest and cheapest, was thinking of just going ahead and replacing that and see if code goes away. But before even doing that I wanted to get others’ opinion whom maybe had this code pop up before.
It's an overly sensitive computer reaction to an 02 sensor readout. It will probably go on and off multiple times after certain numbers of drive cycles but never affect the way the car runs. My 05 V6 sedan with 199k miles is doing the exact same thing. I would just ignore it until the car actually begins to show signs of drivability issues.
 

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Discussion Starter · #11 ·
It's an overly sensitive computer reaction to an 02 sensor readout. It will probably go on and off multiple times after certain numbers of drive cycles but never affect the way the car runs. My 05 V6 sedan with 199k miles is doing the exact same thing. I would just ignore it until the car actually begins to show signs of drivability issues.
So you’re saying to just do nothing? Don’t replace O2 sensor(s)? Forgot to mention that the CEL is not illuminated on the dash. I got the code from the OBD2 scanner. Meaning it’s in memory. Didn’t think about this but should I clear it and see if it comes back?
 

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You should to replace that sensor. If you don't replace that sensor and it turns out that the cat is fine and the sensor was the one that's dead, you can end up shortening the life span of cat. These cars have different tunes build in to condition the cat under different conditions, I'd imagine that bad readouts can possibly ruin the cat.

Not to mention that if your son ever moves to a county or state that requires emissions testing, you'd want to help prevent him from spending any money chasing down an issue that you can solve now.
 
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