"The 1M sub-circuit board is not installed" warning message

I just got this gameboy advance sp (AGS-001) from eBay, and when I put in any game I get a warning message “The 1M sub-circuit board is not installed" and treats the game as if it has no save file.

I figure that this gameboy has been tampered with (as I don't see others with this problem), but I want to know, how do I fix this, and how much would the parts cost?