2.4K views · 38 reactions | [nonda Auto DIY Center] P0420 is the most common engine error code, it stands for catalyst system efficiency below threshold. Check out this self-repair video tutorial created by nonda's expert mechanics. Fix it yourself and save $$$ on your repair fees. Don't forget to claim your FREE ZUS Smart Vehicle Health Monitor here https://bit.ly/FreeZUS-ADC and get an in-depth diagnosis of your vehicle condition. | nonda | Facebook