Looking at the postcognition sense effect in the DC Adventures book (same rules as m&m3e) I noticed it required checks to determine what your visions are that reveal info about the past (DC15 for a confusing symbolic vision, DC30 for a clear matter of fact vision).
What I couldnt find was what you roll against that DC. Since you need 4 ranks in Senses to buy postcog is the roll 1d20+4? is the roll an investigation or perception skill check? if it is the skill check do the 4 ranks of senses add to the skill check as well as the skills normal bonus?
Looking at the main blurb for Senses, the Precog and postcog blurbs and the power descriptor they have set aside in its own box in the senses section tells me nothing about how you make the actual check so a break down of what I roll and what mods apply would be parameters for a good answer, bonus points for page references.