Live Data
Last reported case: 2 weeks ago
Based on 17 owner reports (3 from Reddit, 14 from forums)
What is P0420?
🚗P0420 on 2020 HONDA Accord
This page focuses specifically on P0420 issues reported by 2020 HONDA Accord owners. The experiences and fixes below are from real owners of this exact vehicle.
Symptoms Reported by 2020 HONDA Accord Owners:
vacuum leakstallingcarbon buildupmisfirecheck engine lightburning oil
Parts Often Involved:
catalytic converterso2 sensortransmissioncylinder 3serpentine beltdownpipe 02 sensoroem thermostatpcv valvedonut sparetorque converter
What Owners Say
Real experiences from 2020 HONDA Accord owners
Cost Reportvia reddit_comment
“If it still starts, accelerates, and shifts ok, you can probably ignore some of the stuff they suggested for a *little while*. But honestly, the KBB value of your car is about $850-1000.”View original
Experiencevia reddit_comment
“P0420 is for sure the cat. The transmission needs to be cleaned off, filled to the right amount and add dye to the transmission and drive it couple hundred miles IF it can be driven.”View original
Experiencevia reddit_comment
“That's difficult unless you're in a state that suspends emissions/ suspends emissions on older vehicles. Knock sensor and oil pressure switch are easy swaps.”View original
Experiencevia reddit_comment
“At 250k miles, be ready for it to go soon. If it still starts, accelerates, and shifts ok, you can probably ignore some of the stuff they suggested for a *little while*.”View original
Experiencevia reddit_comment
“The transmission needs to be cleaned off, filled to the right amount and add dye to the transmission and drive it couple hundred miles IF it can be driven.”View original
Fixed Itvia forum_reply
“There is a way to properly diagnose what the problem is but I don't know what it is, have the tools to do it, nor do I have the patience to learn it. The first time I got the P0420 code I read up on what it meant, concluded that the problem could actually be the sensor itself, and decided to throw a new one at it and it worked.”View original
Fixed Itvia forum_reply
“The first time I got the P0420 code I read up on what it meant, concluded that the problem could actually be the sensor itself, and decided to throw a new one at it and it worked.”View original
Experiencevia forum_reply
“If the VTC is replaced mechanics usually replace the chain & tensioner too. I replace the serpentine belt & timing chain tensioners every 100K as a preventive maintenance measure.”View original
Experiencevia forum_post
“After VCM, cylinder 3 misfire comes back and goes away every now and then (P0303). A few months later, now I have a problem with my catalytic converter (P0420).”View original
Experiencevia forum_reply
“Burns a lot of oil which probably did bad things to my catalytic converter hence the P0420. I changed the spark plugs on cylinder 3 today and it seems like the engine is a lot more stable at idle now.”View original
These are real experiences shared by 2020 HONDA Accord owners on automotive forums and communities. Results may vary based on vehicle condition and repair quality.
About This Data
This page aggregates 17 discussions about P0420 from 2020 HONDA Accord owners across automotive communities.
Success rate (12%) is calculated from posts where owners confirmed whether their fix resolved the issue.
Last updated: 1/6/2026