Just like doing "idme bootmode 4002" in 6.2 but working in 6.2.1.
Download the attached fbmode.zip and run:
adb push fbmode /data/local/tmp adb shell chmod 755 /data/local/tmp/fbmode adb shell /data/local/tmp/fbmode adb reboot
Experimental Version 0.9: includes nbmode for setting normal boot (4000) and rcmode for setting recovery boot (5000). Untested, PM me if there's a problem.