tu as fait ? :
First, prepare the /boot directory with up to date boot files (this step is not required if you're using the 2017-04-10 release of Raspbian/Raspbian Lite or a later one):
$ sudo apt-get update && sudo apt-get upgrade
Then enable USB boot mode with this code:
echo program_usb_boot_mode=1 | sudo tee -a /boot/config.txt
This adds program_usb_boot_mode=1 to the end of /boot/config.txt. Reboot the Raspberry Pi with sudo reboot, then check that the OTP has been programmed with:
$ vcgencmd otp_dump | grep 17:
Check that the output 0x3020000a is shown. If it is not, then the OTP bit has not been successfully programmed. In this case, go through the programming procedure again. If the bit is still not set, this may indicate a fault in the Pi hardware itself.
If you wish, you can remove the program_usb_boot_mode line from config.txt, so that if you put the SD card in another Raspberry Pi, it won't program USB boot mode. Make sure there is no blank line at the end of config.txt. You can edit config.txt using the nano editor using the command sudo nano /boot/config.txt, for example.