Hoping someone can help me with this. I have a 1999 Honda Civic. Has 340.000 miles. The catalytic converter has about 120K miles.


I was about to get the car smogged here in Calfornia when the check engine light came on. I can't recall the code number, but the code was saying the downstream 02 sensor system was not working properly. We replaced the downstream sensor and the light came on again within 20 miuntes with the same code. We cleared the codes and the light stayed off. The next day had the car smogged and it passed easily, I think the HCs were below the average. The car measured between 9 and 13 HCs. Two days later the light came on. Now the system is giving a code for bad catalytic converter. P0420.


Any suggestions?