Rep Power: 0

My check engine light has been on for a few months now, however it hasn't made a difference in the performance of my 2005 Honda civic lx. My local mechanic scanned the code and told me it was p0428 and most likely my catalytic converter needs to be replaced. I've been browsing the forums and i've read it could possibly be a faulty o2 sensor... I'm not sure whether to spend 1K on a new cat or try replacing the o2 sensors? Any advice or input is greatly appreciated! Thanks!

 
Rep Power: 367

compare prices and check the least expensive - both will get some 3 digit figures, unfortunately, since 2005 uses wideband o2 sensors

no way to know which one is the culprit? unless ezone knows a trick on that, wait for his input?

 
Rep Power: 0

One way to test the cat is using an infrared thermometer gun and measuring the temperature at the inlet and outlet of the cat while car ideling at normal operating temperature. If the temperature at the inlet is much higher then at the outlet then the cat is clogged

 
Rep Power: 518

The code can't be P0428, it's probably P0420. Cat efficiency below threshold.

There is nothing in the P0420 code definition about O2 sensors or A/F sensors being bad. There are a ton of other codes available specifically for those sensors.

IOW, you will only waste money replacing sensors needlessly.

Trust the code.

 
Rep Power: 0

So getting the cat replaced is my best bet?

 
Rep Power: 518

Probably.

I'd also want to make sure I know why the cat has failed, and I'd want to make sure there aren't any exhaust leaks between the head and the cat.

 
Rep Power: 0

thanks for your help! I'll take it to the dealership in a couple of weeks, and I will update on the outcome.