Yes and yes to questions #1 & #2

That's because the remote is not a "one-trick-pony"...in that it sends out multiple data to 3 different systems:

1. EWS- the immobilizing system
2. FZV - central locking system
3. DWA - anti-theft alarm siren system

And though the 3 systems listed above are independent of each other...there are some aspects/circumstances where they work in conjunction with each other...or communicate with each other. One is not dependent on the other...but can affect the function of one or the other.

The e70 is a new generation BMW which has a much more complicated communication bus than the old gen BMWs (like the e38/e39/e46/e53)...but I'm going to refer back to the old gen BMWs just because their communication bus is simpler. But the foundamental or basic engineering design is going to be the same...but the modules for the e70 is going to be different (as well as slightly more complex).

In the old gen BMWs the remote sends out a 2-way signal for starting the engine (EWS) on a 125 KHz RF (radio frequency)...this system is also self-powered thru induction and does NOT require the battery inside the key. The induction uses the antenna ring around the ignition switch and the EWS transponder inside the key (which also had a copper induction coil in the new style/diamond shaped remote key). There is 2-way communication between the key's internal EWS transponder (remote and non-remote keys) and the EWS control module and DME/ECU. There is an ISN (individual serial number) that was written to these aforementioned components when the car rolled off the assembly line...and BMW keeps that information in a database. At each start attempt...these 3 components (key/EWS-CM/ECU) will check/verify for the same ISN...if they all match, then the car will start. If they don't, then the car's starter & fuel ignition will be shut down.

The FZV & DWA systems communicate with the key over a 315 MHz RF (in North America & Australia) or 433 MHz (in Europe and other markets). This signal is transmitted when the lock/unlock button is pressed on the remote. This signal requires the battery inside the key to be transmitted. The signal is picked up by an aerial embedded in the rear window (on sedans)...or in the rear left cargo window (on Tourings & SAVs). The signal is then sent to several amp/receivers (FZV/diversity/etc) which ends up at the GM (general module)...which then sends commands to lock/unlock and arm/disarm the car.

The FZV (central locking) system utilizes the actuators in each door, trunk, as well as an actuator for the fuel filler flap. The DWA (anti-theft alarm siren system) shares the door & trunk actuators with FZV as well having a hood sensor, interior motion sensor, and tilt sensor.

Again, all 3 of these systems are independent of each other but work in conjunction. So one or more could work while one or more could be down. The e38/e39 fuel filler flap is known to sometimes fail and can blow the fuse in the trunk. This can take down the remote locking & arming system...all because one of the FZV monitors is not working...but the car will still start.

Or EWS could get out of sync with one of the keys and the EWS rolling code table...but the remote key can still lock/unlock and arm/disarm the car.

When you move up to the F chassis BMW models with its more technicallly advanced communication bus...EWS/FZV/DWA is under the control of the CAS/FEM/BDC modules. But again, the same underlying design principles are the same. Start immobilizing looks for info from the remote for the 18-bit encryption key that BMW wrote to the components that regulate starting the car. The CAS, FEM and or BDC modules (depending on model or options) also controls central locking and arming of the vehicle sending commands over the LIN bus to the required modules/systems.

For instance, if you have CA (comfort access)...those remotes are sending a specific signal to the CA aerials to lock/unlock & arm/disarm the vehicle. Those systems have their specific code that will allow those systems to work...and the CAS module is looking for the 18-bit encryption key to start the vehicle. The starting encryption is different from the lock/unlock & arm/disarm encryption...this is how the remote can start the car but not lock/unlock it etc.

This is also why there' an emergency procedure for starting the vehicle when the signal from the remote is not functioning properly...for early models, you insert the remote fob in its slot, then press the START button...in latter BMWS (without the slot) you hold the remote fob up to the little symbol icon on the steering column...then press the START button. (See image below from owners manual) This is similar to the old gen BMWs EWS that get's powered by the ring antenna and doesn't require the battery inside the key. Both the old and new gen BMWs EWS (immobilizing) system is self powered and just needs to be in the presence of its induction components to power the remote up to be able to start the car.

Sorry for the long winded post...but its such a common misperception about BMW remotes...to over-simplify how they operate. There's a lot of things going on with them.

Attached Images

 

__________________
Become a BMW CCA member! Click HERE to join and feel free to use my BMW CCA member #191509 as a referral.

• 2015 f06 650ix GC (Moonstone exterior/Cohiba brown Merino Leather interior)
• 2014 f15 X5 50i (Space Gray exterior/Mocha Nappa Leather interior)