Thanks everyone for the tips. The p0442 code came on for me at around 76k miles on my 2014 Mazda 5. I reset the code and it came back on 100 miles later. I was able to blow a small amount of air through the purge valve. When I got the new one I tested it and could not blow air through. I decided to replace both the purge and vent valve since most of the online info I found said they replaced the vent valve. Hopefully the CEL stays off.