Catalytic Converters: Failure vs. Theft, and What's Covered

A catalytic converter can stop working for two very different reasons: it can fail, or someone can cut it off your car. Each situation leads to a different kind of coverage, and mixing them up can cost you time and money. Here is how to tell them apart and where to turn.

What a catalytic converter does

The catalytic converter sits in the exhaust system between the engine and the muffler. Inside is a honeycomb structure coated with precious metals that trigger chemical reactions, converting harmful exhaust gases into less harmful ones before they leave the tailpipe.

Those precious metals are the reason converters are valuable to thieves, and the honeycomb design is the reason they can clog or break internally.

Why converters fail

A catalytic converter rarely fails on its own. More often, something upstream damages it. Common causes include:

• Engine misfires. Unburned fuel enters the exhaust and burns inside the converter, overheating it.
• Oil or coolant burning. A worn engine or leaking head gasket can coat the converter and reduce its effectiveness.
• Faulty oxygen sensors. They can cause the engine to run too rich or too lean.
• Physical damage. Road debris or bottoming out can crack the internal structure.
• Age. Converters can lose efficiency over many years and miles.

Because the root cause is often elsewhere, a shop should find and fix it. Replacing a converter without fixing a misfire can mean replacing it again.

Signs of failure vs. signs of theft

The symptoms are very different.

Failure usually develops over time:

1. Check engine light, often with a code pointing to catalyst efficiency.
2. Sluggish acceleration or reduced power.
3. A rotten-egg smell from the exhaust.
4. Rattling from under the car, which can mean the internal structure has broken apart.
5. A failed emissions test.

Theft is sudden and obvious:

1. A very loud roar the first time you start the car.
2. Visible cut marks or a missing section of exhaust pipe under the car.
3. A check engine light shortly after starting.

Trucks and SUVs with high ground clearance are common targets because the converter is easy to reach.

Coverage when it fails

When a converter fails, several types of coverage may apply depending on your car's age and the cause.

• Factory emissions warranty. Federal rules require automakers to cover certain major emissions components for longer than the basic warranty, and the catalytic converter is commonly among them. Some states add longer emissions coverage. Check your warranty booklet for the exact terms on your vehicle.
• Extended warranty. Some vehicle service contracts cover emissions or exhaust components, but many do not, and others list the catalytic converter as an exclusion. Read the contract carefully. If the converter failed because of a covered engine problem, how the plan handles that depends on its terms.
• Out of pocket. If no coverage applies, replacement costs vary widely by vehicle. Some converters cost a few hundred dollars, while factory units on certain vehicles can cost much more.

Our page on engine coverage and the fuel system coverage page explain related components that may affect the converter.

Coverage when it is stolen

Theft is not a mechanical failure, so neither a factory warranty nor an extended warranty typically pays for it. Instead:

• Comprehensive auto insurance usually covers theft of parts, minus your deductible. If you only carry liability coverage, theft is generally not covered.
• File a police report right away. Your insurer will likely require it.
• Avoid driving the car long distances without the converter. It is loud, may affect other components and may not be legal in your area.

Ask your insurer what documentation they need and whether they have preferred repair shops.

Reducing your risk of theft

• Park in a garage or well-lit area when possible.
• Ask a shop about an anti-theft shield or cage for your converter.
• Some communities offer programs to etch your VIN onto the converter.
• Set your car alarm to be sensitive to vibration, if it has that option.

How Warranty Wizards can help

We help you compare plans from independent third-party providers and show you whether exhaust and emissions parts are covered before you buy. For theft, check with your auto insurer. To compare warranty options, request a free quote at /get-a-quote/.