Brand New Backup Assist Beeping Proximity Alarm Buzzer Assembly 
Fits 2004-2010 Infiniti QX56
Fits 2005-2014 Nissan Armada
Fits 2005-2014 Nissan Frontier
Fits 2004-2008 Nissan Maxima
Fits 2013-2014 Nissan NV200
Fits 2004-2009 Nissan Quest
Fits 2004-2014 Nissam Titan
Replaces 256407S200, 25640-7S200

This unit is what you're supposed to hear if your vehicle is equipped with backup sensors in the rear bumper and an object is getting close.

If your button to override the backup sensors is lit up all the time and the system doesn't work, there is a very good chance this is the fix. Most of the time the sensors are good, but the speaker is bad.