There is only one file type that uses the .PCSAV extension:
Mass Effect 2 Saved Game
Saved game file created by Mass Effect 2, a galactic action role-playing game; includes the player profile, achievements, and items; may be an auto-saved game created by the software or a user-created saved game; can be edited with Gibbed's Mass Effect 2 or 3 Save Editor, or converted to the .XBSAV format for use on the Xbox.
PCSAV files created by Mass Effect 2 can be imported into Mass Effect 3. However, you must make sure that the ME2 PCSAV files are stored in a save directory with the following location and name format:
C:\Users\[user]\Documents\BioWare\Mass Effect 2\Save\[player_profile]\
The [player_profile] should be in the format Name_##_Class_200212, where Name is the name of your character (e.g., John), ## is the character level (e.g., 30), and Class is the character class (e.g., Vanguard, Infiltrator, etc.). The 200212 code represents the date and must be a valid date string. Now, when you open ME3, choose the Import ME2 Character option and import your player profile.
NOTE: Mass Effect 3 uses .SAV files for saved games.
Updated: November 16, 2012