Last reported case: 2 months ago
Based on 22 owner reports (3 from Reddit, 19 from forums)
What is P0420?
P0420 indicates your catalytic converter is not cleaning exhaust gases effectively, typically triggered by a failing converter or upstream engine issues. This powertrain code is moderately serious and can affect emissions and performance, with Honda vehicles like the Accord and CR-V appearing most frequently in reports. Based on 975 repair cases, the average repair cost is $3847, ranging from $0 to $4700.
Common Causes:
- Failing catalytic converter (most common cause based on code definition)
- Upstream oxygen sensor malfunction
- Exhaust leaks before the catalytic converter
- Engine misfires or rich/lean fuel mixture affecting converter efficiency
Symptoms:
- Check Engine Light illuminated (primary symptom)
- Reduced fuel economy reported by some owners
- Possible lack of power during acceleration
- No noticeable symptoms in some cases beyond the warning light
🚗P0420 on 2010 HONDA Accord
This page focuses specifically on P0420 issues reported by 2010 HONDA Accord owners. The experiences and fixes below are from real owners of this exact vehicle.
Symptoms Reported by 2010 HONDA Accord Owners:
Parts Often Involved:
What Owners Say
Real experiences from 2010 HONDA Accord owners
“I initially bought for $2,500 in 2022. Radio is disconnected because there was an electrical short that kept draining and killing the battery. (Yes, even when the radio was turned off.”View original
“Many of the people on this page were very nice and insightful when I’ve posted on here in the past. A little less than a month ago, I had to get my transmission solenoid replaced on my car.”View original
“Just bought a used 2009 Honda accord with a 3.5L V6. The dealer recommended that I use premium gas in it - there is a p0420 code so he said the "premium gas" was taking care of it.”View original
“The dealer recommended that I use premium gas in it - there is a p0420 code so he said the "premium gas" was taking care of it. I have a feeling he's full of shit lol.”View original
“P0420 Code - 1999 F23A4 Hi all, I usually post issues in the car's thread but since I didn't see a post about this code in the 6th gen section, I figured I would make one.”View original
“p0420 & $600 Bucks later Hey Guys, I have an issue witha 2003 Honda Accord 2.4, with 285,000 kms on it I had the CEL light come on as well as some type of fumes coming into the car when the heater blower was turned on.”View original
“It is from a vent shut valve on the EVAP canister that had a crack in it but was sealed. It was not causing issues so I have left it go for a long time.”View original
“I'm running a 2010 Honda Accord 4 Cyl. at around 105,000 miles. If it weren't for the check engine light turning on, I would not have thought anything is wrong with my car.”View original
“My Accord is the 2006 PZEV version with 92,000 miles. A few days ago I got the P0420 Check Engine Light which stands for Catalyst System Efficiency Below Threshold (Bank 1).”View original
“My car has 118,000 miles on it and has never had a major issue (except oil consumption issue that dealer warrantied). I figure if I am going to pay that much for a CAT why not just get a new system instead.”View original
These are real experiences shared by 2010 HONDA Accord owners on automotive forums and communities. Results may vary based on vehicle condition and repair quality.
About This Data
This page aggregates 22 discussions about P0420 from 2010 HONDA Accord owners across automotive communities.
Success rate (14%) is calculated from posts where owners confirmed whether their fix resolved the issue.
Last updated: 1/5/2026