Subaru code
P0420: on a Subaru
How much to fix P0420 on a Subaru? Typically $430 to $2,325 for catalytic converter replacement, the most common fix. This is an estimate, not a quote.
On a Subaru, P0420 is often linked to oil or coolant getting into the exhaust, which is a sign the engine needs a look. The converter may be the symptom and not the cause.
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 |
|---|---|---|
| Outback | 2005 to 2019 | Flat-four engines carry the converter close to the engine. |
| Forester | 2006 to 2018 | Same engine family. |
| Impreza | 2008 to 2016 | Oil use and head gasket seepage reported. |
| Legacy | 2005 to 2019 | The 2.5 and the 3.6 both appear. |
Common causes on a Subaru
- Head gasket seepage on older 2.5 engines that burns a little coolant or oil.
- Oil consumption on newer 2.5 engines.
- Aging air-fuel sensor.
- Converter built into the front pipe on some models, which makes replacement a full pipe job.
NHTSA's public complaint file shows how owners describe this kind of trouble: the 2012 Subaru Outback has 294 complaints on file, and 32 of them use wording like catalytic, check engine, P0420, oil; the 2013 Subaru Forester has 78 complaints on file, and 24 of them use wording like catalytic, check engine, P0420, oil. Complaints are owner reports, not proof of a cause.
Check this first
- Check coolant and oil levels. Any loss without a visible leak is a clue.
- Ask about white smoke on cold starts.
- Have the sensor waveforms checked first.
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.
On several Subaru models the front converter is part of the exhaust assembly, so the part is big and the price is higher than a bolt-on converter.
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 |
| Head gasket replacement | $1,325 to $3,775 |
Questions to ask the shop
- Is the engine losing oil or coolant?
- Is the pipe sold with the converter?
- Do you offer a warranty?
Got a quote already? Check it against the range. Wondering if a recall touches this problem? See Subaru recalls by model or check a VIN.
P0420 on a Subaru: questions
Will a head gasket be needed?
Only if there is a leak. Ask for a test, not a guess.
Does Subaru offer extended coverage?
Some models had extended coverage on certain engine parts. Ask a dealer to check the VIN.
How much does it cost to fix P0420 on a Subaru?
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, 2012 Subaru Outback
- NHTSA complaints, 2013 Subaru Forester
- 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.