[rjoelshipp]

My girlfriend and I both have BMWs. I have a 2012 328i and she has a 2018 430i. Can I use my 2012 328i fob to also control/drive her 2018 so I don't have to carry two fobs around? I have looked all around and can't find any info on this. Thanks.

[Mashman]

With an existing fob, there is no way, because there is no way to determine the crypto keys for the transponder chip.

With some locksmith tools you might be able to program a new fob first to one car, and then to the other, but this would only be the transponder chip that is used to start the car. I think you would run into issues with the rolling codes of the remote though.

So, while you might be able to start the car, I don't think it would work with remote buttons.

[rjoelshipp]

Thanks for the input!

[Orion4]

Might be possible, but it raises a security issue. Say someone is able to code the FOB as you described, then at a later date, they have a nasty breakup with their GF. They still have access to her car. Potentially a bad situation if anything happens to her car or its contents.

[mstevens]

Originally Posted by Orion4

Might be possible, but it raises a security issue. Say someone is able to code the FOB as you described, then at a later date, they have a nasty breakup with their GF. They still have access to her car. Potentially a bad situation if anything happens to her car or its contents.

Or, much more likely (if this were possible) would be for a parking valet, mechanic, or inspection tech to amass a collection of working keys to our cars, then collect BMW's at their leisure at some future date without implicating themselves.

[Larry77]

Aren't the fobs a different style even? My wife drives a 2012 X5, I drive a 2013 f30, my daughter drives a 2006 e90, all three of our fobs are a completely different generation.

The 2006 needs to be in the dash to start, the 2012 only needs to be in the car but goes into the dash to charge, mine is a battery that you change and does not insert into the dash...no way they can be programmed for more than one of our cars.

[mstevens]

Originally Posted by Larry77

Aren't the fobs a different style even?

Sometimes, but not always. My wife's X3 and my M4 have fobs that are essentially identical. We distinguish them by fingernail polish matching their paint colors (you could use touch-up paint) in the little spots on the back that were originally for colored stickers that they no longer give you.

Besides, there are people who have more than one of the same model or series from the same year.

[Mashman]

First, you would only be able to get the transponder chip working, remote functions can only work with one car, I'm not sure about comfort access. So, even in contemplating it, I would only consider it feasible with a transponder emergency key. Here's a link to emergency key, you can see the different transponder chip types, by series, down in the description. https://www.ebay.com/itm/BMW-Plastic...-/231087587430

Every key, whether Emergency, Remote, or Comfort Access, has a transponder chip in it, and will start the car when inserted in the dash (emergency keys require a holder). There is locksmith tools that will allow you to update the information in a CAS module, but you need information that is stored on the transponder chip. This information is only available if you know the cryptography keys of the transponder chip, which is only available when the chip is first programmed to the car, or if you have a dump of the memory of the CAS unit that the key came from.

So, yes it's possible to have a key that will start 2 different cars. Both (or more) cars would need to use the same type of transponder chips. It will only work with remote lock/unlock/trunk buttons for one car. An expensive locksmith tool would be required. And, there is some risk of damaging the CAS module trying to program it.