What causes a failed catalytic converter in the Hyundai Elantra, and how can it be prevented?

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What causes a failed catalytic converter in the Hyundai Elantra, and how can it be prevented?

Catalytic converter failures are a known problem in some Elantra models, particularly after 80,000 to 120,000 miles. A failing converter can lead to check engine lights, reduced fuel economy, and failed emissions tests. Contributing factors include engine misfires, burning oil, o r contaminated fuel. How can owners prevent premature converter failure, and is it covered under the emissions warranty?

Gari Specialist asked on 21 Jun 2025 18:06:24 pm

1 Answer

13 views |

Gari Master - on 21 Jun 2025 18:08:31 pm

The catalytic converter breaks down harmful exhaust gases into less harmful emissions. Over time, it can become clogged, contaminated, o r damaged.
Causes of failure:

Unburned fuel due to misfires

Oil o r coolant entering the combustion chamber

Long-term exposure to rich fuel mixtures

Physical impact o r overheating
Symptoms include:

Poor acceleration

Rotten egg smell

Check engine light with code P0420 catalyst efficiency below threshold
Prevention:

Fix engine misfires o r oil consumption issues quickly

Use high-quality fuel and oil

Follow regular maintenance schedules
Warranty note:
The catalytic converter is covered under the Federal Emissions Warranty 8 years/80,000 miles in the U.S.