You are probably using one of the Cypress Kits for your project (Which one??)
On the programming part of the Kit is a UART-USB bridge realized which you already use for the laptop connection. The other UART pins are on 5V (or 3,3V, depending on your kit/setting), your GPS module probably on RS232 levels with +-12V.
Those voltages can fry your PSoC!! You will need a level-shifter as the MAX232
Have a look into your Kit's schematic, one of the pins (P0.2 or P0.3) might be in use by some hardware or bypass cap.