Good Morning everybody,
So, I have a 2003 FX4 F150 Extended Cab. Love my truck, the passenger door lock no longer works with either the key fob or the interior buttons. The lock just kind of "stutters" and clicks but will not go up or down. Also, I tried the actual key in the locks, and the drivers door will unlock and lock fine, but, the passenger door does not. The key just turns easily from left to right ?????? Any ideas?
Thanks!

 

You might have to take the door panel off and check the linkage in the lock mechanism to see if it's out if place or broken

 

It might just need a couple squirts of lube... but definitely going to be a problem inside the door... going to have to take off the panel like Darrin said.

 

Probably a failing actuator. Pretty common.

 

+1 on simply taking the interior panel off and lubing the hell out of things, paying particular attention to the door latch mechanism itself. Just lubing up the lock cylinder (if that is what you meant) doesn't do much for an overall sticky mechanism. I often used to purchase (well, before the Cash for Clunkers program eliminated them from the market!) vehicles that needed a little TLC, keep the for a while and fix them up a bit, then turn them for a profit. Sticky "locks" were very common. Often times I'd simply take everything apart, then work each and every component by hand to see what was needing attention.