When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Find which door is causing the door ajar light to come on, then grab a can of WD-40 and spray some into the inside of the door latch and open and close the door a few times. Sounds kind of hokey but it did the trick on mine. If it works it's faster than disassembling the door to unstick the switch. The Ford dealership actually did this to my dad's 2004 F-150 back in about 2006
I tried pb Blaster in all the door latches, even the back ones just cause, and no luck so far.
I got mine from the original owner who had a bed camper in it and used it for the winter. He neglected it a little, letting it sit, and not knowing a whole lot about caring for his vehicle.