P0028 Code on 2011 Outback

starting this off with, i know nothing about cars, talk to me like i’m stupid. I have a 2011 sub outback that about a week ago popped up the P0028 code, i had gotten an oil change about 300 miles before this btw. the reason i noticed is because the check engine, traction control, and brake lights were on; the car itself was running perfectly. after clearing the codes it didn’t come back until today, the lights were on the dash again and the code came up, however this time i had some issues starting my car, it was turning over but not starting til about the third time, any ideas on what needs replaced? can’t afford a mechanic gotta do it myself.