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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > General E90 Sedan / E91 Wagon / E92 Coupe / E93 Cabrio > Spare key question



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      04-11-2013, 07:55 AM   #1
tennis_pr0
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Spare key question

So I have comfort access on my 335i. I was just wondering, if my battery in my key goes dead, would I still be able to get in and start the car with a dead battery? Would it be a good idea to keep my spare key in the glove box?
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      04-11-2013, 07:59 AM   #2
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If you're key battery is dead the car won't see it so no...you won't be able to start the car with it. If you have comfort access it would be a horrible idea to keep your spare in the car...think about that for a minute. I'm not sure the car would lock with a key inside anyways.
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      04-11-2013, 08:12 AM   #3
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Yeah so that's my concern, if my battery dies in my key what do I do?
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      04-11-2013, 08:12 AM   #4
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Quote:
Originally Posted by derryck View Post
If you're key battery is dead the car won't see it so no...you won't be able to start the car with it. If you have comfort access it would be a horrible idea to keep your spare in the car...think about that for a minute. I'm not sure the car would lock with a key inside anyways.
No car won't lock with the key inside.

OP it would be a HORRIBLE idea. First thing a car thieve does after breaking into a car is CHECK the glovebox. I mean damn talk about hitting the jackpot.
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      04-11-2013, 08:13 AM   #5
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Quote:
Originally Posted by tennis_pr0 View Post
Yeah so that's my concern, if my battery dies in my key what do I do?
You should have 2 keys if it dies in one grab the other.

To replace battery
the CA battery is a CR2032, same battery you would use in a desktop PC motherboard.

You pop the key out the back of your fob and use a dime and twist in the thin slot below the key hole, it pops a small cover off the bottom/back of the fob, that is your CA battery.

The battery does not charge when the fob is in the dash.

Positive plus sign faces towards you when inserting the new battery.

THANKS GLIB
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      04-11-2013, 08:16 AM   #6
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Quote:
Originally Posted by Delta0311 View Post
You should have 2 keys if it dies in one grab the other.

To replace battery
the CA battery is a CR2032, same battery you would use in a desktop PC motherboard.

You pop the key out the back of your fob and use a dime and twist in the thin slot below the key hole, it pops a small cover off the bottom/back of the fob, that is your CA battery.

The battery does not charge when the fob is in the dash.

Positive plus sign faces towards you when inserting the new battery.

THANKS GLIB
You mean keep the spare on my keychain. Is it okay to have two keys in the car at the same time?
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      04-11-2013, 08:17 AM   #7
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If the battery in your fob dies who cares. Your fob has a metal blade key inside of it that you can use to open the door. Once inside the car you put the fob into the slot in the dash and the car will start even if your battery is dead.
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      04-11-2013, 08:44 AM   #8
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Quote:
Originally Posted by 2kaccordocoupe View Post
If the battery in your fob dies who cares. Your fob has a metal blade key inside of it that you can use to open the door. Once inside the car you put the fob into the slot in the dash and the car will start even if your battery is dead.
+1
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      04-11-2013, 08:45 AM   #9
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Quote:
Originally Posted by tennis_pr0 View Post
You mean keep the spare on my keychain. Is it okay to have two keys in the car at the same time?
No because if you lose your keys you will be taking a trip to the dealer for spares and I believe they are $100 or more a pop.
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      04-11-2013, 09:01 AM   #10
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You can leave the non-active key in the car. But it's a dumb thing to do. A flat battery will not keep you from getting in the car (using the physical key in the physical door lock) or from starting it (EWS is inductive and does not require key battery power). One more thing: you can expect the replaceable batteries in both keys to fail at about the same time.
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      04-11-2013, 09:22 AM   #11
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      04-11-2013, 07:54 PM   #12
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thanks guys
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      04-11-2013, 09:01 PM   #13
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They used to provide a non powered key

They used to provide a non powered key .
Which actually looks like an old time car key in black plastic.
You can use it to open your door and then put in
a plastic case that looks like the comfort access fob
then you put it in the fob slot to start the car.
My car came with the fob case but I had to buy the key
for 50 bucks.
When the battery goes dead in the fob I believe it will work
the same way.
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      04-12-2013, 03:57 AM   #14
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It's been stated before, but to be clear, it's true of both CA and non-CA remotes. The metal key that pops out of your fob can be used to open the car. The fob, flat battery or not, will start the car when physically in the key slot. A dead fob battery won't strand you.
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      04-12-2013, 07:09 AM   #15
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If you are concerned about it, how about putting a spare fob battery in the glove box? Aren't they like $0.50?
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      04-12-2013, 05:50 PM   #16
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Quote:
Originally Posted by Delta0311 View Post
The battery does not charge when the fob is in the dash.
huh???
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      04-12-2013, 06:10 PM   #17
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Question related to fob... If you change the flat battery does the fob need reprogrammed or does it keep its info even at complete power loss?
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      04-12-2013, 06:39 PM   #18
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Quote:
Originally Posted by Kwik E Mart View Post
huh???
There are two kinds of remotes, Comfort Access and non. Non-CA requires that your key go in the ignition to start the car. When it's there, its internal battery gets charged inductively by the car.

On comfort access, because the key doesn't typically go in the dash, the battery must be replaced manually. It is not rechargeable.

Quote:
Originally Posted by shata View Post
Question related to fob... If you change the flat battery does the fob need reprogrammed or does it keep its info even at complete power loss?
None of the key info is stored in rewriteable memory, much less volatile. So no, it doesn't need reprogramming after a flat battery. As has been stated, you can, in fact, STILL USE THE KEY WHEN IT IS DEAD. The only part that won't work is the remote functionality.
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      04-12-2013, 06:51 PM   #19
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Quote:
Originally Posted by alexwhittemore View Post
There are two kinds of remotes, Comfort Access and non. Non-CA requires that your key go in the ignition to start the car. When it's there, its internal battery gets charged inductively by the car.

On comfort access, because the key doesn't typically go in the dash, the battery must be replaced manually. It is not rechargeable.

None of the key info is stored in rewriteable memory, much less volatile. So no, it doesn't need reprogramming after a flat battery. As has been stated, you can, in fact, STILL USE THE KEY WHEN IT IS DEAD. The only part that won't work is the remote functionality.
Thanks for setting that straight. The amount of misinformation in this thread is impressive. I think the bottom line (and to the OP's original question), you can still get in a CA car and start it with a dead key battery.
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      04-12-2013, 06:54 PM   #20
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Quote:
Originally Posted by SharkBait View Post
Thanks for setting that straight. The amount of misinformation in this thread is impressive. I think the bottom line (and to the OP's original question), you can still get in a CA car and start it with a dead key battery.
No problem. That is indeed the bottom line.

Re: my answer above, I will say this: I don't know one way or the other about BC preferences/radio settings/seat position/car diagnostics. I'd imagine those are in nonvolatile read/write memory and so won't die with the battery, but that specific piece I don't know.
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      04-12-2013, 07:30 PM   #21
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You'll start getting warnings on the dash and notice you have to be really close to the car to unlock it when the battery gets low. The likelihood of sudden death is minimal.
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      04-13-2013, 09:22 AM   #22
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Quote:
Originally Posted by alexwhittemore View Post
There are two kinds of remotes, Comfort Access and non. Non-CA requires that your key go in the ignition to start the car. When it's there, its internal battery gets charged inductively by the car.

On comfort access, because the key doesn't typically go in the dash, the battery must be replaced manually. It is not rechargeable.



None of the key info is stored in rewriteable memory, much less volatile. So no, it doesn't need reprogramming after a flat battery. As has been stated, you can, in fact, STILL USE THE KEY WHEN IT IS DEAD. The only part that won't work is the remote functionality.
O okay thanks for info, I was just asking cause dead battery and complete power loss are 2 different things.
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