Posts Tagged: check engine light flashing

How to fix Code P0420

What is code P0420 Catalyst System Efficiency Below Threshold When attach a trouble code reader and come up with a P0420, your first assumption may be that you need a new catalytic converter, simply because the words catalytic converter are mentioned in the code. After the tests you may indeed discover that the catalytic converter is bad. But first you have to understand how the air/fuel and emissions systems work. How the air and fuel mixtures are calculated The powertrain control module (PCM) receives inputs from the engine coolant temp … Read More