Hi all

Recently, my keyfob has stopped working all but 5% of the time. It used to work really well from afar, but suddenly stopped.
The car is nearly 7 years old, could the battery in the remote no longer be holding a charge (it does recharge while in the ignition, right?)? If so, can it be replaced?
Alternately, is it possible the antenna got messed up/disconnected somewhere? I notice that the keyfob works better close to the passenger side of the car....

thanks

 

Chances are the battery needs replaced. Should only cost you a few $$$'s

 

Can i just crack the remote open? Is there a proper way to do it?

thanks

 

Okay, according to my rep, my key has a lifetime lithium battery that is indeed recharged when it is in the ignition, and once it stops taking a charge, i get to buy a new key.

I'm going to find my spare key, get it working, then do surgery on the dead battery key. Worst case, it doesn't work, no real harm there, since it "needed to be replaced" anyway.

The big question is whether or not the code is stored in non volatile memory or in RAM -- so when i pull out the mostly dead battery, will i lose the state of my rolling code, or will it be fine?

Will post results.

 

I have a 2009 mini convertable and my wifes key drops programing. I changed the battery and reprogramed it and it still drops all remote access and the other programing. Dealer tells me I may need a new key fob, I can't belive that. anyone else with this problem. I have to bring it to dealer on Monday.

 

ericscottf - what happened? I have the same issue and am considering surgery. Unfortunately I do not have a spare key and really don't want to lose all functionality if I take it apart.

 

I haven't done it yet. I've got a lot going on now, I'll get to it soon, perhaps today. Un/fortunately, i have a spare key, so it isn't of extreme urgency...

Will PM you when I have a result!

Eric

 

Sounds sort of like that lifetime/100k miles transmission fluid...

While the recharging feature is cool, they should have created a way to replace the battery without buying a $300 key.

 

I think they did... Just not for our year.

 

Just an update, I opened the key and took pics.
I ordered a new panasonic VL-2020 battery. The stock tabs aren't the same as the ones that came with the battery, but i'll just glue it down and use some wire.

I'll post again when I've put the new battery in and I'll update as to whether or not the key needs to be "re-synched" with the car or if it just works.

If anyone already knows about the re-synching process, let me know. I've seen a few threads about how it either requires a dealer, a sequence of button presses/car starts, or nothing.

edit: hooked up 3v with 2 AA batteries and it worked fine (remote unlock - didn't try starting car). So the rolling code is stored in non volatile memory.

Ordered this from mouser:
http://www.mouser.com/ProductDetail/...fs3uWgMA%3d%3d
It looks like it will be the easiest one to get the leads to work with. Couldn't find one any closer to the factory leads.

 

Okay, using the VL2020-1VC panasonic part works really well.

http://www.mouser.com/ProductDetail/...fs3uWgMA%3d%3d

I was able to make it work without even adding wire. The tabs bent around somewhat nicely (see attached pic)

Cleaned up the excess plastic from when I cut it open and then closed it up with some epoxy around the rim. Positioning the circuit board is easy, there are notches in the board for bosses in the button side that position it properly.

For the record, completely removing the battery and putting a new one in days later doesn't lose the programming for the immobilizer or the remote entry. Seems to be stored in NV memory.

Definitely worth it to replace a 250$+ key!

 

Thank you for posting this! Really good information. Curious, what tool did you end up using to "cut it open" ? Looks like an xacto modeling fine tooth saw would do the trick or an xacto #11?

The main key I've been using finally has exhibited the same symptoms you've had. I switched to my spare key (wife's) and all is well again. I might as well purchase two of these replacement batteries.

(edit...) also, did you have to solder the new battery tabs in or it looks like in the last photo you cut off the old tab leaving a small section to fold over onto the new one?

 

I took a regular utility box cutter with handle and tapped a corner in with a hammer, then tapped it along the edge to cut through. It is held together VERY well, and opening it w/o destroying it or cutting my hand was the hardest part.

The battery from mouser has the tabs welded to the battery - FYI, you have no chance of soldering tabs to a battery, it doesn't work like that. Buy the battery with the tabs.
Remove the old battery by cutting it out and desoldering the tabs from the circuit board and pulling them out.
bend the tabs of the new battery into place and insert it
Then you solder the tabs to the circuit board.

be careful not to short the battery and that the battery is insulated from the circuit board.

good luck!

 

Awesome! Thank you for the follow up on this.

I purchased 2 of the batteries that you specified ($9.44 shipped) and will try my hand using my xacto fine tooth saw blade. I build RC models and the soldering and repairs look straight forward.

 

It really couldn't be much easier, all things considered.

Just keep the following in mind:
1) you want it to be somewhat water resistant when you're done, so seal it with epoxy well, but not so well that you can't open it again in 8 more years

2) if you press the button a lot of times with a low battery and the car doesn't respond, you run the risk of the codes getting out of sync. I don't know what BMW's rolling code look-ahead is, but most manufs is 256.

good luck!