2008 S60 2.5T, 155k miles

Engine system service light came on this week. Car running just fine, no hesitation, steady idle. Had the codes pulled. Cleaned the MAF (it wasn't really dirty). Replaced the air filter (it was dirty). Codes came back. Started to wonder about the PCV. Checked the dipstick...no smoke. Did the balloon/glove test on the oil filler...no inflation.

Should I worry? Not sure. One concern I do have is that I checked the oil last week and it was low. Don't recall this car ever using oil before. No oil spots in the garage, everything under the car was dry. Am I starting to see some engine wear? For now I'm going to put some AT-205 in the oil (in case there's a minor leak somewhere, Scotty Kilmer likes the stuff) and check the oil level frequently.

Any suggestions?