motorola xt926 no fast boot mode

hi
motorola xt926 no fast boot mode

Sorry for my English

I wanted to root my phone but made ??a mistake somewhere.
now the phone is always off. when connected to the computer, program RSD see him as QHSUSB_DLOAD; computer see him as Qualcomm HS-USB QDLoader 9008
RSD don`t flasing(The phone failed to switch to fastboot mode)(FAIL) flasing cabl dont helped.
How reestablished bootloader