I just purchased a 2000 F150 Lariat. The passenger’s door does not want to lock or unlock with the electric lock function or with Key fob. It tries, sometime it does, and sometimes it doesn’t. Seem like it is not getting enough power to pull or push the lock. It locks just fine with auto lock when put into drive and the brake is released. Any ideas?

 

With my 2001, in order to unlock the passenger door with the kep fob I have to double hit the button, with little time between the button pushes. Hope that this helps.

 

In both your cases, sounds like the actuator is going out in that door. Do a search on this site for door lock actuator. I have a 99 and both of mine were acting up. Needs a few seconds in between to "recharge". Replaced acuators (power lock motors), 1 hr, works like new.

 

Correction, door does not lock with auto lock when put into drive and release brake.

I ordered an Actuator, it should be here tomorrow.