Tried several other methods without luck.. undocked, docked and so forth? Still waiting for answer on this one....!
Well, I called tech support and they said to send it in. I decided instead to open it up. I took the screws out. and I had a hard time getting one side and the bottom of the plastic off. So I just held the top open and I could see the plug. I unplugged it. Rebooted machine. Turn off machine. Plugged it back in. Enabled Legacy in Bios. Then installed Bios A16 from the BIOS update off my flash drive. it worked. Thanks for instructions in this post.
I can confirm, disconnecting the CMOS battery for a minute or so corrects the problem and allows the BIOS update to work.
That said, it is impossible to disconnect without removing the bottom case assembly, and as stated in other posts, it is *very* easy to break one or more retaining tabs or such on the bottom case, even with the correct tools (be particularly wary of extremely thin frame parts around the USB port and the upper air vents). If you still have warranty, I would recommend just doing a warranty swap.
I can't get it to work. followed all the steps, strip down the tablet to bare bones and still can't get it to update.
The boot takes almost 1 minuto to show Dell circle. When updating the bios it restarts, black screen for 30 sec and normal boot again. No update was made to the bios.
I'm also without sound on windows 10, it says that device didn't not respond/ativate!!
Can you help?
After trying everything I could find and read about, etc, here's what worked for me.
Disconnected cmos battery, removed all power(battery and power cord). Held power button down for 10 seconds. Waited a few minutes.
LEAVE CMOS BATT DISCONNECTED. Reconnected all power(battery and power cord). Powered up tablet, set everything default in bios, saved and booted to Windows. Started Dell Bios update .EXE and BAM! Updated. Tablet booted to Windows. Shut down and reconnected cmos battery.
BAD CMOS BATTERY. Not having used the tablet for some time the battery died and corrupted the bios I believe. **bleep**.
BUT! No more proximity sensor problem, no more slow start-up, and finally updated bios. So, with all the included warnings, try at your own risk I guess. Good luck.