Last reported case: 3 weeks ago
Based on 4 owner reports (4 from Reddit)
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 SUBARU Impreza
This page focuses specifically on P0420 issues reported by 2010 SUBARU Impreza owners. The experiences and fixes below are from real owners of this exact vehicle.
Symptoms Reported by 2010 SUBARU Impreza Owners:
Parts Often Involved:
What Owners Say
Real experiences from 2010 SUBARU Impreza owners
“She has a 2009 wrx impreza 2.5L turbo and her car is throwing P0420 while trying to get her emissions done. Her cats look fine, however in the picture i included, the uppipe is completely blown.”View original
“Hey all, posting on behalf of my gf. She has a 2009 wrx impreza 2.5L turbo and her car is throwing P0420 while trying to get her emissions done.”View original
“Cleared a P0420 code from my Impreza and drove it 2000 miles across the country no problem. Code still hasn't come back.”View original
“2010 Impreza Outback Sport lifespan I have a fairly high mileage (170k) 2010 Impreza OBS thats currently in the shop getting the head gaskets done, which totally blows, but I really love the car and would like to keep driving it.”View original
“the shop also mentioned that my front control arms are rotted out so I should probably get that done too. I got the car pretty cheap so I'm still willing to throw some money at it but the cost are really starting to add up.”View original
“Code still hasn't come back.”View original
These are real experiences shared by 2010 SUBARU Impreza owners on automotive forums and communities. Results may vary based on vehicle condition and repair quality.
About This Data
This page aggregates 4 discussions about P0420 from 2010 SUBARU Impreza owners across automotive communities.
Success rate (0%) is calculated from posts where owners confirmed whether their fix resolved the issue.
Last updated: 2/9/2026