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Matt, Mechanical Engineer
Category: UK Car
Satisfied Customers: 21727
Experience:  BEng hons Mech engineering, in auto industry 22 years
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BMW: Set alarm with key sender..unlock

Resolved Question:

BMW Mini One. Set alarm with key sender. Key sender switch to unlock then broke. Cannot open car manually without triggering alarm. Have tried manually locking then unlocking but this does not work. Help!
Submitted: 8 years ago.
Category: UK Car
Expert:  Matt replied 8 years ago.

I would suggest that you prise off the battery / back cover to the key to see if you can get to the button contact below the plastic outer button cover. You have to remove the outer cover entirely and underneath you should find either a black rubber button or a pair of metal contacts which are closed by the outer button.
You should then be able to actuate these and disarm the alarm, at which point you can replace the key with a new one.

To program a new key all you have to do is press the lock or unlock button 4 times in quick sucession or switch the igntion on and off then press the lock button and then the unlock button inside of 10 seconds.
Customer: replied 8 years ago.
I have already dismantled the key (I have some electronic knowledge) and found that the unlock button had broken off. I resoldered it into position but it did not unlock the car. The button was not firm and soon came away again. I tried bridging the remaining connections with two pins but to no effect. The strange thing is that now the locking button on the key circuit board no longer has any effect. I have unlocked the driver's door manually with the key but pressing the lock button on the key doesn't relock it. Throughout these operations the alarm warning light on the end of the steering wheeel stalk continues to flash.
Expert:  Matt replied 8 years ago.

This sounds like the key fob circuit is now damaged and has probably sent some odd signals to the car ECU in its death throes.

Its going to have to be a trip to the dealership for a new key I'm afraid, typically they'll need to see the registration document before they can cut you one to match your existing lock.

You should then be able to re-programme the key as I detailed above.
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