Samsung GT-s6312 USB issue connecting to USB My samsung GT-s6312 phone does not connect to PC. Even after connecting USB cable, it gives an error to download software.
I found that most of the time such type of problem are solved by this link.

STEPS : (for Windows specific instructions):


Ensure phone is not connected to PC.
Uninstall KIES from PC. Reboot your PC and Reinstall KIES after that. Just for great measure... open KIES, go to Tools | Troubleshoot connection error. Follow instructions and wait for it to finish the troubleshooting procedure.
Reboot your phone (or turn off and then on your phone again). Do not connect it to your PC just yet.
Once rebooted, go to your phone's dialer, type *#7284# - A configuration window will appear. In that window's USB section, if it's default to PDA, tap MODEM, then back to PDA, (if it is MODEM in the beginning, change it to PDA) then press the back key to exit. Most importantly, it must set as PDA when you exit.
Turn off USB debugging in your phone.
(Optional) Set your phone's screen timeout to a lengthy time. (minimum 1-2 minutes - recommended 5mins to 30mins) its found in Settings | Display. You can change this back later on.
Connect the phone to your PC with USB cable and let windows load your drivers... and wait for the drivers to get reinstalled.
Once reinstalled, disconnect the phone off USB. Switch USB debugging back on in your phone settings, and reconnect the phone back - you'll see windows load another set of drivers for your phone. Wait until it is completed. (This step is a precautionative measure to ensure your phone is identified with all the necessary drivers)
Once complete, unplug your phone, and turn off USB debugging... This is to ensure MTP will initialize. Also, press the phone's home key until your homescreen is displayed. Only after doing all that, reconnect your phone back to PC.
Test and see if MTP works using Windows Explorer. You'll see your phone's USB storage and SDCard contents if it does.


Hope it will help you..