Bmw 325 ci coupe sport problem wth pasenger lock locks with remote but wont unlock any ideas thanks?

Transponder or battery problems wouldn’t affect just one door.

The fault lies inside the door. Most likely a faulty solenoid or problems with the connecting rods between the solenoid and the lock. The rods run through plastic guides and with age they get brittle and can break. As the rod has to pull and push, it’s entirely possible that a broken guide is allowing the rod to flex when it tries to push to unlock the door.

It could also be that the mechanism just needs lubricating and is too stiff at the moment for the solenoid to overcome the friction when it tries to unlock that door.

Whatever the cause, the door card and the moisture barrier (plastic sheet: peel it back carefully, and tape up any tears when you put it back) have to be removed to get a good look inside.

Try replacing the remote battery first.  No luck, it could be a bad fob or a bad transponder in the car or a bad lock cylinder.  Try a spare remote.