Here is a re-direct to another site, edmunds would rather us to not answer questions this way, although i have found quite a few good answers by surfing the internet and i have found a lot of sites that have added to my in shop library.
Go to :
http://www dot justanswer dot com/questions/qmir-2000-nissan-frontier
In addition to this answer may i suggest that you get a service manual for your car and an electrical diagram so you can find the different components in the system.
A factory manual will tell you how to test the parts,,,,,an aftermarket manual may not.