Catalytic Converter Repair: Signs, Causes and Options

What it does

The catalytic converter is part of the exhaust system on most modern vehicles. It uses a catalyst made of precious metals, such as platinum, palladium and rhodium, to convert harmful exhaust gases (carbon monoxide, unburned hydrocarbons and nitrogen oxides) into less harmful carbon dioxide, water vapor and nitrogen. Those metals are also why converters are a theft target.

Why converters fail

A converter usually fails for a reason. A misfire, a rich fuel mixture, or oil or coolant entering the exhaust can overheat or contaminate it. Repeated short trips can also keep the exhaust from reaching full temperature. We find the cause before replacing the converter so the new one does not fail the same way.

Signs of a failing converter

• A check engine light, which may flash if misfires are severe
• Reduced power or poor fuel economy
• A sulfur or rotten-egg odor
• Rattling from underneath the vehicle
• Rough running, hard starting or stalling when the converter is badly clogged

What repair involves

Replacement often requires cutting or welding, and the oxygen sensors may need testing or replacement. A vehicle with a failed converter can fail an emissions test. In California, most replacement converters must be CARB-approved for your vehicle, so the right part depends on your make, model and year.

Next steps

If the check engine light is flashing, avoid hard acceleration and heavy loads, drive as little as possible and have the vehicle looked at promptly, since severe misfires can overheat and damage the converter. Our ASE-certified technicians can inspect your vehicle and explain your options. Book at whichever of our shops is most convenient.