P0420 Hyundai Accent 2010-2017 Oxygen Sensor Problem

In this video, I explain how to diagnose and repair fault code P0420 (Catalyst System Efficiency Below Threshold) on a Hyundai Accent (2010–2017) caused by an oxygen sensor issue. You’ll learn how to use a scan tool to identify the problem, inspect the downstream oxygen sensor (B1-S2) and its wiring, test the sensor with a multimeter, and replace it if necessary. I also show how to clear the fault codes and verify the repair with a road test. This step-by-step guide will help you restore your car’s efficiency and resolve this common check engine light issue.