Q: Getting error code P0304

Since you are getting a misfire code on the #4 cylinder that will cause the computer to shut off these other systems. The misfire needs to be fixed first. Most of the time when this comes up it is caused by a failing spark plug or ignition coil. A mechanic would typically inspect and test these first before going further. If these parts are fine then a compression test will typically be done to see if there are any internal engine problems. I’d recommend having a mechanic determine the cause of your engine misfiring issue in order to make the repairs needed.