Last reported case: 1 months ago
Based on 15 owner reports, 15 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 2020 TOYOTA Tacoma
This page focuses specifically on P0420 issues reported by 2020 TOYOTA Tacoma owners. The experiences and fixes below are from real owners of this exact vehicle.
Symptoms Reported by 2020 TOYOTA Tacoma Owners:
Parts Often Involved:
What Owners Say
Real experiences from 2020 TOYOTA Tacoma owners
“So I am confirming again that replacing the knuckle fixed the issue, after putting a little time and miles on the new bearing. I will also add some more closure to this topic by addressing more of the symptoms I listed in my original post.”View original
“Still tight, quiet, and working as it is supposed to. So I am confirming again that replacing the knuckle fixed the issue, after putting a little time and miles on the new bearing.”View original
“Each time i've scanned and cleared the code it has come back within a few miles of startup and driving. The truck is coming up on 180K so I am at the point that it is just time to replace the cat altogether given the mileage and its the original one.”View original
“Any tips, suggestions, etc. before I purchase and go at this? Checked with a shop just for an idea and got quoted at $1800 so that's not coming out of my pocket.”View original
“Hi all, Way after the fact on this update... I bit the bullet and bought new cats for the whole truck from rockauto.com . along with the O2 sensors for roughly $1100.”View original
“I bit the bullet and bought new cats for the whole truck from rockauto.com . along with the O2 sensors for roughly $1100. Still steep but compared to a shop to just do one for almost $2K definitely the choice to make!!”View original
“I believe my issue was caused by a misfire I had at the same time. That code has not come back and I don't currently have the P0420 either so that's good.”View original
“The latest test I did showed the data from sensor 2 downstream, but not sensor 1. Sensor 1 showed nothing (0.0 volts) from the OBD Link MX+ whether driving or sitting still. 275,000 miles.”View original
“Came back with code P0420 and what the title states. I replaced my catalytic converter and entire exhaust system at 151,000, and I’m currently at 154,000.”View original
“If cheap aftermarket (particularly from Amazon / ebay ) it wouldn't surprise me at all if it's shit. If you have no exhaust leaks 95% of the time it's a failed converter, O2 and AFR sensors are rarely the cause of a P0420/430.”View original
These are real experiences shared by 2020 TOYOTA Tacoma owners on automotive forums and communities. Results may vary based on vehicle condition and repair quality.
About This Data
This page aggregates 15 discussions about P0420 from 2020 TOYOTA Tacoma owners across automotive communities.
Success rate (13%) is calculated from posts where owners confirmed whether their fix resolved the issue.
Last updated: 1/20/2026