Kia Troubleshooting Questions? Ask a Mechanic
Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.If you are reading 17 volts with the engine running that usually means the alternator is overcharging and that can cause all sorts of issue including blowing the headlight bulbs. A normal charging system should never charge more then 14 volts. Before you replace any thing I would consider taking care of the charging system and in most cases that means the alternator is failing.
The code P0420 is the bank to Catalytic converter failure (firewall side) . In 99% of all cases replacing the HO2S will not cause this code to set. The bank 2 converter is not going to come out from the top, it has to come out from under the car. Unfortunately Kia dose not offer any replacement steps.