P0420 In Honda Civic or any other car

Question

Just want to know about P0420 code in any car and specially in Honda. Does that mean only that catalytic convertor is bad or any other reason too?

Answer 1

P0420 is an OBD2 standard code that is universal across all car brands & models. The code indicates the catalytic converter is below the efficiency threshold the car's computer is expecting. The most common cause for this is a bad catalytic converter. However, there can be other sources for this issue including:

• bad O2 sensor
• leak in the exhaust system
• faulty spark plug(s)
• leaking fuel injector(s)
• faulty air/fuel sensor

Answer 2

Another way to check the P0420 code to see if your converter has lost oxygen storage capability is to scan the catalytic converter oxygen sensor and watch the sensor activity. If it fluctuates between 200 -800 millivolts, the same way as a zirconia oxygen sensor fluctuates, this is pretty good indication oxygen storage capability is gone. OBD 2 monitors the activity between the upstream sensor and the catalytic sensor for this very reason, watching sensor activity. Ensure catalytic converter totally warmed up. See this case study at picoauto.com Dodge Ram 2003 Dated 11/05/2015.