Kia Troubleshooting Questions? Ask a Mechanic
Hello, what model and year Kia is this?
P0455 is just a code for a large evaporative emissions system leak, usually when the gas cap is loose or the gasket for it is not good any longer, nothing that would cause a stalling or hard start issue. The P0342 is a code relating to the camshaft position sensor. Most likely it is a bad sensor, but the wiring will need to be inspected to be sure. A faulty camshaft position sensor can cause the vehicle to not start because the computer uses the relationship between the camshaft sensor and the crankshaft sensor to determine where the engine is and when to fire the spark plugs/injectors. I would suggest first repairing the camshaft sensor issue and seeing if the problem happens again.
If my answer has helped you, please help me by rating or accepting my answer. This does not cost you any more, it just allows me to be credited for my work. You can always ask follow up questions after rating or accepting. Thank you.