Parasitic Drain/Dead Battery solved?
 

My X5 has had starting trouble that has gotten progressively worse over the last 6 months. Here recently I had to jump start the car every morning. The battery and electrical system were checked out and everything was fine. The battery is less than two years old.

I have already replaced the FSR and was not sure what the culprit could be. I have spent hour here trying to figure out the problem. Now, I think I have my solution. I disconnected the TCU after reading that it may cause the drain. I am please to report that the car started right up this morning. I do not have bluetooth or bmw assist, but the remote entry is now dead. Looks like I will have to buy a new one.

I hope this helps you forum members with future parasitic drain issues because it has been driving me nuts for months.

TCU?....... Traction Control Unit? Trailer Connector Unit? Tiny Chinese Ukelele?

Telematics Control Unit

:thumbup: I was kind of hoping it was the Ukelele

:rofl:

I am of course planning to replace it with a tiny Chinese ukelele. :thumbup:

+1 :D

:thumbup:

wow way to go off topic

Can you go into more detail as to what you mean by your "remote entry is now dead"? Are you referring to your remote key's functioning...or are you referring to the entire keyless entry part of your cars FBZV (central locking) system?

If you mean your remote key...does your other key work? If it does...have you tried reinitializing both keys?

If you mean your entire keyless entry system doesn't work...does the regular central locking system work (the interior central lock/unlock button on the center console, or using the key manually in the lock cylinders)...and if you do lock the vehicle manually with the key using the lock cylinder...when you walk around to the fuel filler door flap...does it lock or remain unlocked?

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