2015 SONIC CODE P0420

[Emma’s sonic]

Thank you @31003 for posting your troubleshooting technique and how you found the leak. I have a 2013 1.4L (~170k miles) that intermittently sets the P0420 code. I replaced the front pipe ~5years ago because the bellows had a crack in it. I will see if the weld has broken on the newer pipe. There's nothing more aggrivating than having that little yellow engine light come on.

Hi, and sorry to jump in so late. But which pipe exactly do you mean by front pipe? Is this the pipe just before the cat?
Thanks in advance

Ray

 

[cherokeefrogg]

So I got the P0420 code on my '15 LT Sonic about two years ago. I replaced the O2 sensors and had to replace the cat/manifold combo due to a hole; the insides were broken. It lasted a couple of months, then the code returned. I've honestly just let it go. I have the parts to try the spark plug non-fouler to see if the extra distance gives it the reading it likes, but haven't tried it yet. I've put a lot of miles on it with the P0420 code and haven't really seen any negative effects, or none that I've noticed yet. I have a new lead on what may be causing it. My variable valve timing (VVT) solenoids are making noise and I guess are bad; someone told me that today. After a Google search, it seems like they have a chance of being the culprit. That, or ignorant wishful thinking.