I failed chem 1a03 and im planning on going into PBN my 2nd year. i got a 7 in psych 1x03 and i'm doing really well in 1xx3. Is it still a good idea to redo chem during the summer even though it is not a pre-req?

If chem isn't a requirement for the PNB program, I wouldn't worry about re-taking it. However, remember that almost all of the second year entry programs require a minimum average in order to be accepted in to them so if your chem mark is bringing down your average, I would take a course in the summer.

How about you speak to an academic advisor?

I recommend talking to Ann Hollingshead, the PNB course coordinator, and to an academic advisor in your faculty. Good luck!