[MDB 535xi]

I suspect it is a blown fuse but not sure how to map the fuse to the key fobs. I've also replaced the batteries in the keys.

Fuses are located in the rear compartment I know but can anyone can point me to a map laying out the fuses and what each is for? Additionally, the door locking system and trunk opening are all working via the internal unlocking buttons...just the keys are not working. Help, please.

[Qsilver7]

The remotes don't have a "fuse" that powers them. The central locking system is operated and powered by multiple control modules...the CAS module probably being the major module for lock/unlock...along with the FRM (footwell) module and JBE (junction box electronics) module.

The system is kind of complex in that it's not a one trick pony. Depending on how the vehicle is optioned...it can vary in multiple ways in which the vehicle can be locked/unlocked. There's also an encryption that is VIN specific for EWS (start immobilization) and CA (comfort access) which is why a group of BMWs can be all parked next to each other but only the remote with the same 128-bit encryption can be used to lock/unlock as well as start with the remote fob. The encryption makes each remote & car specific to each other. Hopefully you have the original remote fobs that came with the car from the factory...and not replacements that are aftermarket copies.

There's the manual cylinder in the driver's door which communicates over a bus directly to the CAS module to unlock. If you have CA (comfort access) you can lock/unlock the door by touching the ridges on the door handle (as long as you have a remote fob on your person)...this system uses multiple CA aerials that are located around the car which picks up an encrypted signal from the remote fob, that goes to a remote control module, that then sends data to the CAS module to lock/unlock the vehicle. Then there' the buttons on the remote fob that also will send an RF (radio frequency) signal that is picked up by an aerial embedded in the rear windshield...that signal is sent to an amp/receiver which then sends the data to the control modules to lock/unlock the vehicle.

All the above is just to paint the picture that your issue may or may not be something simple. If the central locking system is working by using the buttons inside the cabin, then there's a communication issue with your remote fobs...but where the failure is...can be varied. Diagnostic software or apps may be able to pinpoint where a breakdown in communication is occurring.

BTW, most BMWs of the F chassis era, have a fuse index chart folded up and stored in a slot in the rear fuse box...is your missing or perhaps overlooked if you didn't know it's supposed to be there?

The pics below show the location of the fuse index charts found in my (f06) 650ix GC and (f15) X5:

[Qsilver7]

Central locking system Info:

[MDB 535xi]

Thank you @Qsilver7. Really appreciate the information and expertise. You bet I looked for the 'fuse info card' but did not find it in the glove compartment or rear compartment, as you pointed out. Looks like this may be bigger than a fuse AND bigger than something I can handle. Will likely need to head to the dealer :-(

[MDB 535xi]

Hey @Qsilver7](contact:327547) after visiting my local BMW dealer, I'm told they want to try replacing the 'Keyless Entry - Antenna' with remote control receiver module located under the rear spoiler and then 'retest'. This part alone is US$975. What say you, please.

[Qsilver7]

Originally Posted by MDB 535xi

Hey @Qsilver7](contact:327547) after visiting my local BMW dealer, I'm told they want to try replacing the 'Keyless Entry - Antenna' with remote control receiver module located under the rear spoiler and then 'retest'. This part alone is US$975. What say you, please.

It’s not about me…it’s about you. How do you feel spending $975 and it turns out that it’s not the cause of the issue? Are you comfortable spending that amount of money for a “try”?

Not that the remote control receiver isnt the culprit…but in trouble shooting this issue…are you prepared to spend money on attempts to narrow down the actual culprit? It’s great if the first try hits the target…but what if it misses the mark?

The remote fobs do send a signal to the aerial which then sends data to the remote control module…which then passes that communication off to the CAS module. So it is a possibility…are they getting a diagnostic trouble code that indicates that the remote control receiver is not receiving or sending data over the LIN bus?