The TCU controls the remote keyless entry function. I have to use the key manually in the door to lock/unlock. The lock button in the center console works fine.

I hope this EWS/DWA/FZV info helps explain what I was trying to say
 

I know I'm new to the X5 forum...but I'm shocked to find out that the TCU (tranny control unit? or telecommunication control unit?) handles the function of the central locking system/keyless entry system (FZV/FZBV) on the e53 X5.

My understanding based on the other BMW models built during this time frame (E46/e38/e39/Z3/etc)...the central locking system/keyless remote system is controlled by the GM (general module). I'm on a steep learning curve for the E53 X5 if this system operates differently on this model.

The remote key utilizes 3 different systems that work in conjunction with each other...but are indeed 3 distinct systems:

1. FZV/FBZV = central locking/keyless entry
2. DWA = anti-theft alarm siren system
3. EWS = immobilizing system (shuts down ignition/fuel/spark/etc)

Also...I inquired about a situation that you didn't respond to...and that is...when you lock your vehicle manually with the key (from outside)...when you walk around to the fuel filler door...is it locked, too...or can it still be opened? If it can still be opened...that may be an indicator that your central locking system has a fault...thus is causing the whole keyless entry system not to operate properly.

Report back about the fuel filler door.

You can also see in the Communication Bus Topological Chart below...that the keyless entry (FZV) and anti-theft alarm siren system (DWA) is connected to the GM as its major control module:

Fuel filler door locks and unlocks with the rest of the locks. I can lock/unlock the doors with the key in the door and the button on the center console, but not with the remote buttons on the key. This function was working fine until the tcu was disconnected.

Incidentally, I bought a used TCU off of ebay. It came from a 2007 Z4. It plugged right in and the bluetooth function paired right up with my iPhone and works great. It did not fix the keyless entry though. Anyone know if I need to have the dealer reprogram to get the keyless to work with the new TCU?

Got it figured out. Did the key reset procedure and everything works fine now.

great...glad you got it sorted out