Honda Catalytic Converter: Symptoms, Theft, Cost & Replacement

The catalytic converter is an expensive part to replace, and it’s also a target for thieves. Whether you’re looking at a P0420 code, dealing with a sudden loud exhaust, or just want to protect the converter you have, this guide covers the warning signs of a failing Honda converter, why converters get stolen, what affects the replacement price, and how to decide what to do next.

What the catalytic converter does

The catalytic converter sits in your Honda’s exhaust and turns harmful gases into less harmful ones before they leave the tailpipe. Inside is a honeycomb coated with precious metals: platinum, palladium and rhodium. Those metals are exactly why converters are both expensive to buy and worth stealing.

Symptoms of a failing Honda catalytic converter

• P0420 (or P0430) check engine code — “catalyst system efficiency below threshold.”
• Sluggish acceleration and poor fuel economy as a clogged converter restricts exhaust flow.
• A rotten-egg (sulfur) smell from the exhaust.
• A rattle from under the car as the internal honeycomb breaks apart.
• A failed emissions/smog test.

If you’re seeing a P0420, read the full P0420 guide first. A bad oxygen sensor can mimic a failing converter, so make sure you aren’t replacing the cat to fix a sensor problem. A basic OBD2 scanner lets you read the code yourself before spending anything.

Why Honda catalytic converters get stolen

Thieves cut converters off and sell them for the precious metals inside. Signs yours was stolen: a sudden, extremely loud roar when you start the car, plus a check engine light. To reduce the risk, you can fit an anti-theft shield or cage, park in well-lit areas, and have the converter etched with your VIN.

What affects the replacement price

The price depends on the model, whether you use an OEM or aftermarket part, and labor in your area. On older, out-of-warranty Hondas, one option is a quality aftermarket catalytic converter. Just make sure it’s emissions-legal in your state. Confirm the converter is truly the problem (and not an O2 sensor) before buying.

Can you drive with a bad catalytic converter?

If the check engine light is steady, Honda says to avoid high speeds and have the vehicle inspected immediately. If the light starts flashing, stop safely. A clogged converter chokes the engine, hurts performance and fuel economy, and can overheat. And if the converter failed because of an underlying misfire, continuing to drive makes everything worse. If the converter was stolen, the car will be extremely loud and will fail emissions, so get it replaced promptly.