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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Mechanical Maintenance: Break-in / Oil & Fluids / Servicing / Warranty > Key wont remote unlock



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      07-01-2019, 03:08 AM   #1
slay2k
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Question Key wont remote unlock

So I've had some "low keyfob battery" lights in the dash a few months ago and was able to fix that by charging my 2007 335i keyfob (which has a rechargeable battery) on top of my toothbrush charger.

One day I walked up to the car and wasn't able to open the doors. None of the buttons worked. I used the slide-out key and was able to get in, start and operate the car. Afterwards, the remote functions worked for a few days and then would die again, suggesting a dying battery. I got a replacement VL2020 battery off eBay and managed to desolder the old one and re-solder the new one. But now the remote keys have stopped completely, including after driving the car whilst opening it with the slide-out key.

Would the car start without battery power in the keyfob?

I've been told there's no reprogramming that needs to be done, but I guess I could be wrong. Perhaps my soldering job was faulty? I could use some help from anyone who has ideas or has gone thru this before.

Thanks boys!
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      07-01-2019, 04:47 PM   #2
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Bump.

I've confirmed that the key works in the ignition without a battery. I put the old battery back in and charged it in the idling car for about 15 minutes, but the remote keyfob buttons still don't work.

In the past, they would work for a day or two after a recharge. Now I can't open or lock the doors from the remote with either battery.

Ideas?
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      07-02-2019, 12:10 AM   #3
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Have you got a chance to scan your car for any codes as yet? I'd start there.
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      07-02-2019, 06:03 PM   #4
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Yes, no codes thrown.
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      07-15-2019, 07:43 AM   #5
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You just might need a New Rechargeable Battery in your Remote.
check this video:
CR2032 Battery.
Listen to comments in the video at the 3:23min Mark.

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      07-15-2019, 11:30 AM   #6
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My remote doesn't have a replaceable battery compartment. The entire thing is sealed and had to be cracked open to try and replace the battery, which requires de-soldering work.

In spite of all that, it still fails. I'll be sending it in to repair to someone who does these repairs.
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      07-24-2019, 07:01 PM   #7
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Has anyone been able to start the car with bad batteries? My car starts but the key fob does not lock the door. Does it make sense to replace the battery even though the car starts with this battery? Thank you.
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      12-18-2019, 11:39 AM   #8
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Did anyone get a resolution on this. One of my keyfobs on my 2008 E70 X5 wouldn't open the central locking today but would start the car when it was in the dash holder.
I used the spare to open the car and then drove using the original just in case it was the battery needed recharging.
When my wife drove the car it was fine on the way to work, but on the way home the car just went into neutral and stopped.
We tried the spare key again and this works as normal. certainly points to a key issue, but since the spare key was used, everything seems to have reset (time/bluetooth/radio stations/sat nav). I know change in key can be programmed to individuals but I never thought it would behave like the battery had been disconnected.
Anyone else seen this behaviour?
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      12-18-2019, 03:50 PM   #9
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I ended up mailing my key to Scott @ bmwgm5. He fixed and returned it, not sure what the problem was but something was definitely failing over time.
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