The check engine came on and I got a PO420, i searched it up and it’s an exhaust/catalyst code.
recently I’ve been driving and waves of what smells like exhaust or probably gas get into the cabin and I was wondering how I would be able to fix it. People say it’s the catalytic converter and others say it’s the o2 censor but I don’t know. Any tips would help!

 

Hello,

Here is a thread on diagnosing P0420 code, but considering that there is a considerable exhaust smell, it's likely the catalyst that is starting to show its age. Here is a thread on selecting the catalyst as a replacement.

Hope this helps and best of luck!

 

I get a catalyst code every year when I travel on holiday and always when on the highway doing highway speeds.

So weird since it will probably be next year when traveling when I will see the code again.

 

Huh, could be a sign of something bigger than just a bad catalysts, I would look a little more into it. There could be a chance that the mixture is off by a little bit, which is more noticeable at higher RPM, and considering the age of the catalyst, it may have a tough time keeping up with increased demand. Other theory is that they may be blocked or partially obstructed, causing less exhaust to actually reach the catalyst.

Start by checking Live Data, see what the output for Downstream sensors you will get compared to Upstream ones, here is a recent thread showing a good example of what I presume to be a fried O2 sensor, though it is yet to be confirmed as of right now. See how the sensors behave at Idle, how quickly both Upstream and Downstream sensors respond to throttle input, and what results you will be getting at the highway. Other thing you can try is measuring the Temperature of the catalysts at the inlet and outlet to see if they are clogged at all, here is a thread with a video that describes the process.

Hope this helps and best of luck!