Can a coil pack cause the p0420 check engine code?

Question

I have a 2008 Pontiac Grand Prix 6 Cylinder. There was a day where my car wouldn't start. My father replaced all 3 coil packs, and it did not start. It was then sent to a mechanic, who then replaced (from what he said) a chaft drive sensor. After that, It had a very rough idle. Then the mechanic replaced one or two of the coil packs, (cant remember). Ever since, the check engine light has been on with the code p0420. Is there a possibility that it could be a coil pack? I am not going to the same mechanic, my dad took it there while I was working, and my car was broken into there. I replaced my Gas Cap, and used fuel injector cleaner.

Answer 1

If it had a misfire, it can damage the converter. So, it is likely the converter needs to be replaced to resolve the problem. So, yes the coil can cause the code, but because the engine was misfiring and dumping raw gas into the converter.