Honda code
P0420: on a Honda
How much to fix P0420 on a Honda? Typically $430 to $2,325 for catalytic converter replacement, the most common fix. This is an estimate, not a quote.
On a Honda, P0420 shows up after 100,000 miles more often than before. The converter may be fine and a front sensor may be reading wrong, or the converter may be worn. The order you check matters, because the converter is the costly one.
General meaning of P0420: The computer compares the oxygen sensor before the catalytic converter with the one after it. On this code the two readings look too alike, which suggests the converter is not cleaning the exhaust as well as it should on the side with cylinder 1. See the full P0420 page.
Models to know about
| Model | Years | What to know |
|---|---|---|
| Accord | 2008 to 2017 | Four-cylinder Accords are the bulk of the cases. |
| Civic | 2006 to 2015 | The small 1.8 engine runs hot and loads the converter for years. |
| CR-V | 2007 to 2016 | Check the engine oil level too, since oil burning shows up as a bad converter reading. |
| Pilot | 2009 to 2015 | V6 models have two converters, so bank matters. |
Common causes on a Honda
- Front air-fuel sensor drifting with age, which makes the computer misjudge converter efficiency.
- Rear oxygen sensor that reacts too slowly after 120,000 miles.
- Exhaust leak ahead of the rear sensor, which feeds it outside air.
- Worn converter. Honda reports it more when oil burning or misfires happened earlier in the car's life.
NHTSA's public complaint file shows how owners describe this kind of trouble: the 2010 Honda Accord has 581 complaints on file, and 32 of them use wording like catalytic, check engine, P0420, emission; the 2010 Honda Civic has 397 complaints on file, and 3 of them use wording like catalytic, check engine, P0420, emission. Complaints are owner reports, not proof of a cause.
Check this first
- Check engine oil level. Burning oil coats a converter and kills it.
- Listen for ticking on a cold start that fades. That is an exhaust leak.
- Ask whether the rear sensor waveform was checked, not just the code.
Wide range: this job varies a lot. Itemize your quote for a better answer.
How this range is built
| Part of the job | Low | High |
|---|---|---|
| Parts | $300 | $1,900 |
| Labor: 1.2 to 2.5 hours × $110 to $150 an hour | $132 | $375 |
| Fees: shop supplies, disposal, diagnostics | $0 | $40 |
| Total, rounded | $430 | $2,325 |
The hourly rate is the BLS Occupational Employment and Wage Statistics, May 2025 average pay for this trade in the US, $27.13 an hour, times 4 to 5.5 to cover what a shop bills (overhead, tools, insurance, profit). Parts are a band from budget aftermarket to the manufacturer part. In California and New York, parts cost more because those states require a California-certified converter. Full method.
Not a repair shop, estimates only. Typical range, estimate. Not a quote. Your car, parts and shop change the number.
Honda converters from the dealer cost far more than universal-fit ones. In states that follow California rules, only approved converters can be used. Ask which applies in your state.
Other repairs that may be involved
| Repair | Typical range, US |
|---|---|
| Catalytic converter replacement | $430 to $2,325 |
| Oxygen sensor replacement (one sensor) | $100 to $350 |
Questions to ask the shop
- Did you test the rear sensor, or just the code?
- Is a CARB-approved converter required in my state?
- What is the warranty on the part and labor?
Got a quote already? Check it against the range. Wondering if a recall touches this problem? See Honda recalls by model or check a VIN.
P0420 on a Honda: questions
Is my Honda converter under warranty?
The federal rule covers some emissions parts for up to 8 years or 80,000 miles. Check your booklet and ask a dealer.
Can I drive with P0420?
Yes, but the repair gets costlier if misfires or an exhaust leak continue.
How much does it cost to fix P0420 on a Honda?
The most common fix, catalytic converter replacement, has a typical range of $430 to $2,325 across the US. That is an estimate built from parts prices and local labor wages, not a quote. Your model, engine and shop move it.
P0420 on other makes
Sources
- NHTSA complaints, 2010 Honda Accord
- NHTSA complaints, 2010 Honda Civic
- NHTSA recall lookup by VIN
- US federal emissions defect warranty rules (40 CFR part 85, subpart V)
Written from public NHTSA data, owner-reported patterns and general repair knowledge, in our own words. Model lists are examples, not a full list, and patterns are not a diagnosis. Prices updated October 2026. Not a repair shop, estimates only.