Re: Door ajar sensor
a few things to check.
Look at the catch, not on the door itself but on the truck. If it is loose, or has moved, the door will close but will not trigger off the door ajar. Move it back to the original location by lining it back up with the original circle in the paint and tighten it back up with an Allen wrench.
If the latches are fine and you can also try Electronic Component lubrication, which yuo can get at Radio shack or in most electronics stores. First Spray all your door latches, including the rear hatch with some type of cleaner. Then spray with a can of compressed air to clean off and dry. Next spray with the lube and open/close doors a few times. This is really only a temporary fix for some, but has worked well for others.
You can also replace the switch itself. This will cure the problem 99% of the time, it will cost a little more, but should fix your issue. There is a switch in the lock/latch mechanism of the door itself where the latch on the body clicks into. It wears out and goes bad from time to time. Replacing this should no doubt clear up your problem.