Engine & warning lights
What Is a Catalytic Converter and How Do You Know It Failed?
How a catalytic converter works, why they get stolen in the US, failure symptoms, and realistic replacement pricing.
The short version
US pricing: a federally compliant aftermarket unit is $250–$700; CARB-legal California units $550–$1,400; an OEM converter $1,100–$2,800.
- 5 symptoms you can check yourself
- 5 diagnosis steps in order
- 4 FAQs answered directly
- Last editorial review: 2026-09-10 · 9 min read
Top 3 facts
- A P0420 or P0430 code (converter efficiency below threshold).
- Chronic misfire melting the honeycomb substrate.
- Read codes first: P0420 does not automatically mean a dead converter; a lazy downstream O2 sensor can cause it.
- With a low-efficiency converter, temporarily yes. With a plugged one, no — back pressure kills power, raises temperatures and can damage valves. You will also fail emissions testing.
Cost table
US pricing: a federally compliant aftermarket unit is $250–$700; CARB-legal California units $550–$1,400; an OEM converter $1,100–$2,800. Labour is 1.5–3 hours ($150–$400). Realistic totals run $450–$1,500 on a typical car and over $3,000 on some V6s with two converters. Anti-theft shields cost $150–$350 installed — far cheaper than a stolen converter.
Figures are a guidance range calculated with a published method — read the methodology.
Run your own estimateWider context
A catalytic converter is a metal canister in the exhaust containing a honeycomb substrate coated in platinum, palladium and rhodium. Its job is converting toxic gases — carbon monoxide, unburned hydrocarbons and nitrogen oxides — into carbon dioxide, water and nitrogen. Those precious metals explain both its high price and the wave of thefts across the US in recent years.
Early indicators
Sources of failure
- Chronic misfire melting the honeycomb substrate.
- Oil or coolant consumption poisoning the precious metals.
- A persistently rich mixture from a bad O2 sensor or leaking injector.
- Normal age: 100,000–150,000 miles on most vehicles.
- Theft — especially Toyota Prius, Honda Element and lifted trucks.
Steps you should not skip
Read codes first: P0420 does not automatically mean a dead converter; a lazy downstream O2 sensor can cause it.
Watch live O2 data: the upstream sensor should switch rapidly while the downstream sits nearly flat around 0.6–0.8 V.
Test for restriction by measuring exhaust back pressure — over 3 psi at higher rpm indicates a blockage.
Compare inlet and outlet temperature with an infrared thermometer: the outlet should read 50–100 °F hotter.
Fix the root cause (plugs, sensors, oil consumption) before buying a new converter, or the new one will fail too.
Most asked
Can I drive with a bad catalytic converter?
With a low-efficiency converter, temporarily yes. With a plugged one, no — back pressure kills power, raises temperatures and can damage valves. You will also fail emissions testing.
Do catalytic converter cleaners work?
They can slightly help a converter lightly fouled with carbon ($15–$30), but they cannot repair a melted or broken substrate. Treat one as a cheap test, not a fix.
Why was my converter stolen?
Because the rhodium and palladium inside sell for more per ounce than gold. A thief needs two minutes with a saw and gets $50–$250, while replacement costs you $800–$2,500.
Is it covered by warranty?
US federal emissions warranty covers the catalytic converter and engine computer for 8 years or 80,000 miles. Check your vehicle's age before paying out of pocket.
Yearly prevention plan
Fix misfires immediately, never ignore oil consumption, fit a shield if you live in a high-theft area, and park in lit areas.
DriveMet review
US pricing: a federally compliant aftermarket unit is $250–$700; CARB-legal California units $550–$1,400; an OEM converter $1,100–$2,800. Fix misfires immediately, never ignore oil consumption, fit a shield if you live in a high-theft area, and park in lit areas.
What we verified
- Cross-checked 5 warning signs against 5 likely causes before publishing.
- Reviewed 5 repair steps and confirmed the order a shop would follow.
- Compared the cost range with our published methodology and refreshed it on 2026-09-10.
- Answered 4 questions people actually search for on this topic.
Reviewed by the DriveMet editorial team on 2026-09-10 under our editorial policy. This is an editorial review of the page, not visitor ratings.
Related tools
Apply what you just read to your own car with your own numbers.
Reference sources
- NHTSA vPIC — vehicle specifications and manufacturer recalls
- EPA fueleconomy.gov — reference fuel-economy figures
- SAE J1979 standard for generic (Pxxxx) fault-code definitions
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