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Honda Odyssey P0420 code error

AhsokaTanoIC534

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Joined
Mar 15, 2025
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2
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Virginia
Got a honda odyssey P0420 code catalytic converter issue popping up on my CR-V with 180,000 miles.. it started after filling up at a gulf station not sure their gas is top-notch.. scanner showed super high fuel trims like 45% short-term and 35% long-term.. cleared the code filled up at my go to station and it stayed off trims dropped to normal around 10%.. then with a near-empty tank i added 3 gallons at turkey hill and the light came back.. filled up again at another good station and itss gone.. research says P0420 can come from crappy gas like wrong octane, maybe below 87 or low fuel pressure messing with trims.. this actually happened years back too.. probably the gas is the problem and those sketchy stations both in rough, dirty areas, itmight be watering it down or selling low-octane as higher, like 85.5 as 87..
 
Got a honda odyssey P0420 code catalytic converter issue popping up on my CR-V with 180,000 miles.. it started after filling up at a gulf station not sure their gas is top-notch.. scanner showed super high fuel trims like 45% short-term and 35% long-term.. cleared the code filled up at my go to station and it stayed off trims dropped to normal around 10%.. then with a near-empty tank i added 3 gallons at turkey hill and the light came back.. filled up again at another good station and itss gone.. research says P0420 can come from crappy gas like wrong octane, maybe below 87 or low fuel pressure messing with trims.. this actually happened years back too.. probably the gas is the problem and those sketchy stations both in rough, dirty areas, itmight be watering it down or selling low-octane as higher, like 85.5 as 87..
my guess is that this has something to do wirh the temperature. is it cold where you are now? Happened to my ody before wherein the temp was low and that when this code showed up.
 
P0420 error code and high fuel trims are likely from bad gas at random gas stations causing poor fuel quality. Since the code clears after filling at trusted stations, its probably not the catalytic converter but the fuel itself causing the issue
 
Totally agree with you there! If your engine seems to perk up after you switch to better gas, it's probably the fuel quality that's throwing off your trims. You're definitely smart to be mindful of where you fill up, good call
 
So, my 2012 Honda Odyssey threw a P0420 code after I filled up at some rinky-dink gas station during a road trip. The van felt kind of weak

The weird thing is, after I got gas at my usual spot a few days later, the code just went away. The fuel readings were a little off when it happened, So I think the cheap gas messed things up instead of it being a real problem with the catalytic converter
 
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