The lock pump is not as prone to failure, before I would replace it I would lube the mechanism in the door that is giving you issues. The pump is under the passenger rear seat. There is a wonderfull tool called MIghty-Vac it allows you to draw a vacuum and a guage to see if it bleeds down due to a leak. The locking pumps also serves the lumbars, gas door , headrests in non elecric situations, back up rods, and sometimes the trunk handle, it also provides back up vacuum when the engine does not for the HVAC. It runs forward for pressure and backwards for vacuum. Pressure to unlock vacuum to lock, but it could be the other way