"Please do take note that Lenovo Y400 require WLAN card with security code in the firmware & the require model number must be listed in the BIOS. Unfortunately neither Intel Wireless Ultimate N6300 or Intel Wireless Advance N6235 is NOT LISTED in the Y400 BIOS so you will have to either :-

A. Install a BIOS that is updated with the require model.
B. Install a circumvented/modified BIOS which bypass the security check.

Most Lenovo laptops comes with a security feature which will only allow WLAN cards with security code in it's firmware & models listed in the laptop BIOS to prevent data theft (eg snooping). This is an important feature for business user but some non-business users see this as non-upgrade friendly so they normally flash the laptop BIOS with a 3rd party updated BIOS or unlocked/bypass/modified BIOS.

If you install a 3rd party BIOS with updated WLAN models, you will retain the security function but you will still need the respective WLAN card with the security code in the firmware aka LENOVO approved version. However if you install an unlocked/bypass/modified BIOS, you basically remove/disable the security function so you should get the generic version which can also be use on Dell, Acer, Sony etc."