I have a 1999 F150 extended 4x4 and the driver side power lock will only lock by pushing the peg down or with the key. It won't lock by using the passenger side button but the passenger side locks using either button. Any suggestions of what to do are appreciated. I have done some reading and nobody has my exact problem. Have oiled the inner workings to no avail.Could it just be a dirty actuator?Thanks

 

Sounds like the other symptoms posted here, problem with the lock actuators.

Some have cleaned them, others just replace.

 

Where is the actuator...in the door? Thank you.

 

Yes it is in the door.