the pump under the seat controls your lumbar, the backup assist
rods, it provides vacum for the climate control, and the locking function, On a SEC I think it also controls the seat back latching. I have not heard of too many sources for a rebuilt, and getting one from a recycler could get you another with a short life. The last numbers I heard were around $300, you dont need the adapter plate that some try and sell unless the now offer a universal pump, there is a difference between them depending if you have vacum or power headrests.
Operate the locks, if you hear the motor run, you could be lucky and just have a vacum leak, and it could be the hose in the pump. The pump provides pressure or vacum depending on the closing or opening, and times out if it can not perform the function. I would shop dealers for the best price, there are some who discount to the public, check the "Star Mag"