I am from Dell Social Media and Community.
I am sorry to know you have an issue with your system keyboard.
Follow the link http://support.dell.com/support/topics/global.aspx/support/kcs/document?docid=277550#Notebook_Keyboard
Select the "Keys on the Keyboard Is Typing Characters Intermittently or Not at All" under Issue 1
These will be the basic steps for you to confirm keyboard functionality.
Test the hardware by running the 32 bit diagnostics option that is available on the one time boot menu (by clicking F8 after powering on your system, use a external keyboard)
You will be able to test the keyboard under custom test.
If you still have an issue after following the above steps, try using user's manual to unplug the keyboard and connect it back again and verify the functionality.
Let me know if this was helpful or if you need any further assistance.