Question

What happens if you don't get this code P0420 repaired? Will the car stop working?

Answer 1

P0420 Catalytic below effieincy Bank 1

The engine will not shut off, the purpose of the catalytic is to remove harmful emission byproduct  emitted from the engine exhuast, unless the catalytic or exhaust is plugged the engine will run sluggish, the but the car will not stop working