Key Fob doesnt lock/unlock Doors or Trunk

[andrewwynn]

There are decent YouTube videos online. The sequence is similar to this: put in the first key turn to "on" not start then remove the key while holding the lock button and keep it pressed while tapping the unlock button 3 times. (I might have the buttons backwards).

You need to have the doors closed and cenral lock either locked or unlocked I forget which but it can't be in the middle the system will toggle the door locks on to confirm I just never remember if you start locked or unlocked but it won't work if backwards.

The antenna must have power and the correct procedure to test is confirm an output square wave signal when it received a command from the key. When not working the main wiring problem is through the rubber boot going from hatch to body wires will break in that bundle.

Odds are good you just didn't follow the procedure or the key is not working because the button switches have failed or the solder joints have failed inside. Do you have more than one key?

You can test the key atcsome stores that sell batteries: home Depot for example, they have a device that lights up when it senses the signal from a key.

Otherwise find my key repair thread where I have a photo of where to measure the key voltage with needles. If you measure voltage while pressing buttons, it will drop a little while holding the button (example: 3.1 drops to 3.0). No drop, button or solder joints failed.

You need both lock and unlock buttons working to program the key/s.

I start by making sure the buttons are working by measuring voltage then run the relearn procedure. If it doesn't work you probably have a wiring problem to the dv amplifier.

[Algold415]

Originally Posted by andrewwynn

There are decent YouTube videos online. The sequence is similar to this: put in the first key turn to "on" not start then remove the key while holding the lock button and keep it pressed while tapping the unlock button 3 times. (I might have the buttons backwards).

You need to have the doors closed and cenral lock either locked or unlocked I forget which but it can't be in the middle the system will toggle the door locks on to confirm I just never remember if you start locked or unlocked but it won't work if backwards.

The antenna must have power and the correct procedure to test is confirm an output square wave signal when it received a command from the key. When not working the main wiring problem is through the rubber boot going from hatch to body wires will break in that bundle.

Odds are good you just didn't follow the procedure or the key is not working because the button switches have failed or the solder joints have failed inside. Do you have more than one key?

You can test the key atcsome stores that sell batteries: home Depot for example, they have a device that lights up when it senses the signal from a key.

Otherwise find my key repair thread where I have a photo of where to measure the key voltage with needles. If you measure voltage while pressing buttons, it will drop a little while holding the button (example: 3.1 drops to 3.0). No drop, button or solder joints failed.

You need both lock and unlock buttons working to program the key/s.

I start by making sure the buttons are working by measuring voltage then run the relearn procedure. If it doesn't work you probably have a wiring problem to the dv amplifier.

Thanks for the ideas. I will open up the remote and check the buttons for continuity. Also, will try to check the continuity for the diversity antenna wire.

In regards to key for re-learning procedure, if I'm not mistaken, you might be mentioning a procedure for the older generation BMWs. In the E70, when you insert the key fob into the dash, only the trunk button remains visible, so there's no way to hold the 'Lock' or 'Unlock' button when removing the fob, since it's hidden in the cradle.

Will take a look at your key repair thread. Appreciate all the help!

[Mark H]

It’s a nightmare isn’t it Algold? My situation continues without resolution, my fob is working good at the moment as the car has dried out following a period of a month with no rain.
I believe my problem is due to a leak from the sunroof, have you checked for water ingress?
It could be the same issue as mine, but yours is still wet, do you have the panoramic sunroof and is it working and sealing well?
I posted in your thread earlier by accident when I was comparing issues with your post!
Have you read my thread for similarities? Key fob and comfort access.
https://xoutpost.com/bmw-sav-forums/...rt-access.html

[Algold415]

Originally Posted by Mark H

It’s a nightmare isn’t it Algold? My situation continues without resolution, my fob is working good at the moment as the car has dried out following a period of a month with no rain.
I believe my problem is due to a leak from the sunroof, have you checked for water ingress?
It could be the same issue as mine, but yours is still wet, do you have the panoramic sunroof and is it working and sealing well?
I posted in your thread earlier by accident when I was comparing issues with your post!
Have you read my thread for similarities? Key fob and comfort access.
https://xoutpost.com/bmw-sav-forums/...rt-access.html

Hey Mark, I doubt I have the water leak issue that's affecting the module/harness. There is a panoramic roof but it looks to be sealing pretty well. But I will definitely check. My remote never worked since I bought the car and unfortunately I only got one key fob. I'm busy with another project but once that's fixed, I will get back to addressing the key fob. Planning to check signal/button functionality & continuity. Thanks!

[Algold415]

UPDATE:

I went to the local auto parts store and found the key fob RF/battery testing machine. Pressing all buttons lit up the tester so the key fob is functional & battery is good.

What I'm not completely sure about is, if the car starts and operates fine when the key fob is inserted in the dash, does that mean that it's propertly coded to the car's CAS. Or does locking/unlocking and starting/running the vehicle different functions of the programming?

How can the key start and run the vehicle but not be able lock/unlock the alarm (if the diversity antenna is functional).

[andrewwynn]

Usual reason is solder joints have failed on the remote buttons section.

Both of my keys suffered this fate. I was able to cut open my key and reflow the solder and get both to work.

If one of the switches fail you can no longer program the key to the car.

There is a guy that will refurbish a key for about 1/3 the cost of a new one.


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[Algold415]

Pretty sure the buttons are all good, as I stated in my previous post.

[andrewwynn]

Yes and no. The button test is good. My buttons worked yet key did not. I could get my key to work from inches from the car but not 30'. Suggests that the solder joint not working was to the antenna.


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[andrewwynn]

The test (I've read) for the key taking to the car regardless the programming is the OUTPUT from the diversity antenna. It's a square wave I believe.

I just found my fluke scope meter and plan to figure this out myself since my remote stopped working on my car. I lost one of my keys or I'd have taken it apart to reflow the joints again but after I get a replacement I'd do that.

I have a clone car in my wife's so I'll do some readings from her's (working key) and mine with her's and my keys. I'll report what I find.


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[Qsilver7]

Originally Posted by Algold415

What I'm not completely sure about is, if the car starts and operates fine when the key fob is inserted in the dash...:

1. does that mean that it's propertly coded to the car's CAS...
2. Or does locking/unlocking and starting/running the vehicle different functions of the programming?

Yes and yes to questions #1 & #2

Originally Posted by Algold415

How can the key start and run the vehicle but not be able lock/unlock the alarm (if the diversity antenna is functional).

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.