P0420 Code Symptoms

How your car behaves when the P0420 code is active. Sometimes the check engine light is the only sign.

Key Symptoms to Watch For

This is the most common and often the only symptom. The light will illuminate and stay on until the code is cleared.

If the catalytic converter is clogged, it can create backpressure, making the car feel sluggish and slow to accelerate.

When the engine isn't running efficiently due to the exhaust restriction, it will burn more fuel to compensate.

A failing catalytic converter can't properly process sulfur in the gasoline, leading to a distinct hydrogen sulfide smell from the exhaust.