What does fault code P0420 mean?
2 Answers
Fault code P0420 indicates that the catalytic converter system efficiency is below the threshold. Possible causes include the use of leaded gasoline damaging the converter, issues with the oxygen sensor, exhaust pipe damage, or catalytic converter leaks. Related information is as follows: 1. Meaning of P0420: To resolve this fault, it's essential to understand that P0420 (Catalyst System Efficiency Below Threshold Bank 1) means the ECU monitors the efficiency using sensors installed before and after the three-way catalytic converter (TWC). 2. Introduction to Catalysts: The effect caused by catalysts in chemical reactions is called catalytic action, and catalysts are also known as promoters in industry. The composition, chemical properties, and mass of the catalyst remain unchanged before and after the reaction; its relationship with the reaction system is like that between a lock and a key, exhibiting high selectivity (or specificity).
Last year, my car suddenly showed a trouble code P0420, and I was really confused at the time. After checking, I found out it was a catalytic converter efficiency issue, meaning the exhaust wasn't clean enough. It's usually caused by the converter itself aging and clogging or the oxygen sensor failing. Bank 1 refers to the front exhaust section of the engine. My fuel consumption suddenly skyrocketed, and the shop found out the downstream sensor was severely carbon-fouled. Replacing it fixed the problem. This incident reminded me not to ignore such codes when they appear—small issues can turn into big ones. For example, an exhaust leak can also affect performance. Regularly checking the exhaust system during maintenance can prevent unexpected breakdowns on the road. Spending a little now is much better than major repairs later.
