How to troubleshoot a code P0420 on a Ford Focus?

I have a 2012 Ford Focus and recently the check engine light came on. I took it to the mechanic and they said it's showing a code P0420, which is related to the catalytic converter. What could be causing this issue and what steps should I take to fix it?

First, try inspecting the catalytic converter for any physical damages. If it looks okay, then it could be a faulty oxygen sensor. I would highly recommend taking it to a different mechanic for a second opinion and possibly replacing the sensor.

I had the same issue with my Ford Focus and it turned out to be a loose gas cap. Make sure to always properly tighten the gas cap after filling up. If that doesn't fix the issue, then it could be a problem with the exhaust system and you should bring it to a mechanic.

Try resetting the code by disconnecting the car battery for a few minutes. If the code still comes back, then it could be a sign of a more serious issue. I would suggest taking it to a trusted mechanic who specializes in Ford vehicles.

Before spending any money on repairs, try using an OBD-II scanner to get more specific information about the code. This can help narrow down the issue and save you from unnecessary expenses. If you're not comfortable doing it yourself, you can always take it to a mechanic.