note: Some devices like the Huawei K3715 seem to require AT-commands to be typed in capital letters!

There are a couple of options for disabling and re-enabling the following USB-components of Huawei USB-modems:

• modem (M)
• NAND-flashmemory drive (CD)
• microSD-drive (SD)
• PC UI interface (UI)
• network adaptor (N)
• smartcard (SC)

To disable or re-enable those components run the following AT-command, where n is one of the numbers from the table below:

AT^U2DIAG=n

On some models it is possible to read the present value of the parameter n by sending command:
AT^U2DIAG?

n	M	CD	SD	UI	N	SC	remarks	supported by	not supported by
0	+			+				E1750
1	+	+
3	+			+		+	won't work on devices without SC*
5		+		+	+		won't work on devices without N*
9		+			+	+	won't work on devices without N & SC*
10	+	+				+	won't work on devices without SC*
12		+		+	+		won't work on devices without N*
255	+	+	+	+	?	?	reset to factory defaults	K3715, E160E, K3565	E176, E1762, E1750, E173
256	+		+	+			for most devices: everything enabled except the flashmemory; microSD-drive will be available under Windows even without drivers installed	K3715, E160E, E1762, K3565, K3765, E1750, E173 ,E160E	E176
257	+	+	+
259	+		+	+		+	won't work on devices without SC*	E176
261		+	+		+	+	won't work on devices without N & SC*
265		+	+		+	+	won't work on devices without N & SC*
266	+	+	+			+	won't work on devices without SC*
267		+	+		+		won't work on devices without N*
268	+	+	+	+			won't work on devices without N*	E1750, K3565, E173
276	+	+	+	+	+	?	reset to factory defaults	E1762, K3565, K3765, E173, E1750

*) note: Smartcard (SC) and network adaptor (N) are not present in many Huawei devices. Using an AT-command that activates SC or N on a device without these components, will result in errors and so will be noneffective.

Modems supporting AT^U2DIAG? command: E173, E1750 ,E160E
Modems not supporting AT^U2DIAG? command: K3565

Also on some models it is possible to display a list of devices present in a USB-stick, by sending a command:
AT^GETPORTMODE