Use car or BMW connect to find missing keyless entry fobs?

:ugeek: I think I need an uber geek for this one....I cannot find my main set of keys which holds my keyless entry fobs for my 2016 i3 REX and the 2018 X1. (I also have another set of fobs.) I don't know if I dropped the keys between the car and house, inside the house or -- worst case -- I left them in the house door lock and someone lifted them. If I don't find my keys soon, I expect I need to re-key everything.

OR -- THIS IS MY QUESTION: is there any way to get my cars to "call" to the remote if it happens to be inside my house or garage? Or a way to use the BMW connect to do that? You'd think if my remotes communicate with my cars, it may work the other direction? Or is this science fiction? Thanks. I continue to hunt.

Nope. The fobs have no speaker, so even if there was a way to initiate reverse communication, there's nothing you could do to make it findable.

Some cars have two-way key fobs with some sort of sound generator, but not the i3.

Look in to a Tile or similar to put on your key fob.

CharonPDX: Interesting. Thanks.

And I just found the keys. In house, in the side of a box that I thought was sealed!!!

After I posted here I found an article on line that said "it's possible to build your own transmitter [to track the remote], but it would take a lot of time, money and engineering know how..." That author too suggested putting a tracker on the key rings. Which I am going to do.

I'm going to disagree with that article. You can build a receiver using a ~$20 USB SDR (software-defined radio) dongle and a notebook computer with some free software, and then walk around watching the frequency waterfall graph until you locate the missing key fob.

I have SDRs on Raspberry Pi computers grabbing my weather station sensor data, monitoring my alarm system wireless sensors, and even tracking overhead airplane locations via ADS-B. Others are using them to track ship movements in harbors, listen in on police radios, and even decode weather satellite images.....

vreihen said:

You can build a receiver using a ~$20 USB SDR (software-defined radio) dongle and a notebook computer with some free software, and then walk around watching the frequency waterfall graph until you locate the missing key fob.

Click to expand...

Does a fob transmit continuously or must it receive a signal before it responds? I've left our i3 fobs in a drawer for up to 9 months without needing to replace their batteries which makes me think that a fob doesn't transmit continuously. If that's true, how would your SDR detect a fob?

I ASSumed that it is sending out some sort of radio "ping" every few seconds, but it would prevent the use of a pure receiver to locate the missing key fob if it wasn't transmitting.

From reading way too many i3 CarFax reports during my search, I noticed that dealerships seemed to be replacing i3 key fob batteries at about the 3-year mark like clockwork. My late-2015 car had low battery warnings for both fobs when I picked it up, and I told the selling dealer not to bother replacing them because our dog's doggy door collar transmitter uses the same 2032 cells as the key fobs and I have a bulk supply at home. Considering that I routinely get 8-10 years out of the remote non-fob key batteries (all smaller than the 2032) in all of our other vehicles, I made the assumption that it was sending out periodic transmissions.....

vreihen said:

I ASSumed that it is sending out some sort of radio "ping" every few seconds, but it would prevent the use of a pure receiver to locate the missing key fob if it wasn't transmitting.

Click to expand...

If I were designing fob logic, I don't know of any reason for it to transmit periodically. Maybe I'm missing something.

The fob doesn't care is its car is nearby, but a car with Comfort Access cares if its fob is nearby. Press a fob button and it transmits a relevant signal. The fob doesn't care if the car receives its signal and responds because the fob doesn't indicate car state. However, when the door handle of a Comfort Access car is touched appropriately, the car could transmit a signal asking the fob to send the credentials that would cause the car to unlock the door or hatch. If no or incorrect credentials are received, the car remains locked.

Maybe someone with fob programming experience could explain why periodic transmissions would be necessary.

I have misplaced my 2012 535i remote key and the dealership wants 570 plus shop time. I have read about the USR SDR and a way to possibly find it. Can I use a iPad instead of a notebook. What free apps do I need to download? thanks

WHen I lost one of my fobs, it cost around $350 at the dealership. THey required a copy of my registration and license, and ordered it direct from BMW parts. It did not require any shop time. I just took it home and registering it to the car was easy (don't actually remember now what I did, but the dealer did not have to do anything to it or have the actual car). So, look around, or maybe call some other dealers. I can't believe the price has gone up that much in the last couple of years. Once you're validated as the real owner, BMW will make a new fob for your car.

Now, prior to this, I asked the dealership to disable the lost key from the memory in the car. They did that for free. As I remember it will only hold a couple of remote signatures. So, you must have a working fob, or the controller in the car and new fobs must be bought as you have to have at least one working to be able to program the next.