2005 Chevy Malibu trouble code fixs

The 420 code most likely means that you need a new cat. Convertor. The other 2 kind of go hand in hand.
If the injector isn't working properly, you'll get a misfire on that cylinder.
Take a look the wiring harness for the injectors. Look where it goes around the side of the engine, sometimes it will rub through and come in contact with the metal bracket for the purge solenoid.
If nothing there, follow the harness around to the front of the intake. You'll see a bracket that holds the harness, check and see if the harness rubbed through there and broke any of the wires.
The #2 injectors wire colors are:
pink, and light green with a black tracer.

Let me know how you make out with them.