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Car Auto Repairs of Texas

Guide · 6 min read

How to Tell If Your Catalytic Converter Is Bad

The short answer

A bad catalytic converter shows up as a rotten-egg (sulfur) smell, sluggish acceleration, rattling under the car, reduced fuel economy, and a P0420 or P0430 code. In Texas emissions counties it also causes a failed inspection. Replacement typically costs $900–$2,500.

Symptoms, codes, tests, and replacement costs for failing catalytic converters. This guide covers Catalytic converter failure symptoms; What kills catalytic converters; Catalytic converter theft in Texas so you can describe the problem and decide what to check next.

Exhaust & Catalytic Converter Repair: a closer look

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Illustration of a technician using a diagnostic scanner

Computer diagnostics

A fault code identifies a system to investigate, not necessarily a part to replace.

Illustration of a battery tester connected to car battery terminals

Battery testing

Battery testing is one part of investigating starting and charging concerns.

Illustration of a technician inspecting a vehicle on a lift

Hands-on inspection

A hands-on inspection helps connect the driver's symptoms with the vehicle's condition.

Illustrative images, not customer repair photographs.

Catalytic converter failure symptoms

Sulfur smell, dark exhaust smoke, a glowing-red converter after driving, rattling from broken internal honeycomb, loss of power on hills, and the check engine light.

What kills catalytic converters

Converters rarely fail on their own. Engine misfires, burning oil, coolant leaks, and bad oxygen sensors overheat or contaminate them. Fixing the root cause first prevents the new converter from failing too.

Catalytic converter theft in Texas

Converter theft is common in Houston, Dallas, and San Antonio. If your car suddenly roars on startup, check underneath. Anti-theft shields and etching your VIN onto the converter help deter thieves.

Need exhaust & catalytic converter repair?

Loud exhaust, rattles, failed emissions, and catalytic converter replacement. Typical cost: $150 – $450 muffler · $900 – $2,500 catalytic converter.

See our exhaust & catalytic converter repair service →

Frequently asked questions

Briefly, but a clogged converter can cause overheating and engine damage.

No — O2 sensors and exhaust leaks can trigger it. Testing confirms.

Comprehensive coverage usually does.

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