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Old 08-10-2019, 09:04 PM
666 666 is offline
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Location: San Francisco
Join Date: Jan 2017
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Mein Auto: 2010 X3 Xdrive Sports
Key wouldnt start the car

Both of my x3 key remotes stopped working a while ago.
Replaced battery on spare and it didnt help.
I purchased replacement keys from amazon.

Now. I programmed one of this amazon uncut keys using one of the suggestions on the web(there are millions of those). Remote works fine. Then I pull out module and glued it with the spare key . Remote works. But now that spare key(original from bmw) wouldnt start the car.

What gives?
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Old 08-11-2019, 12:47 AM
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Q4 Q4 is offline
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Mein Auto: 2008 x3
I'm not quite following what you are saying you did but:

There are two separate systems on each key.

1. The RF remote system that the buttons use to lock/unlock the car (and open the tailgate). This system is easily programmable by the owner.

2. The RFID chip that is picked up by a coil antenna in the ignition switch itself that initiates a handshake with the car's ecu and tells the car that it's okay to start the engine. In most cars this RFID chip is a passive chip that doesn't require a power source and can be swapped out from one key to another by physically removing it and glueing it into the new key. The grey plastic valet key that comes with our cars uses this type of chip. The black "diamond" keys that have the lock/unlock buttons on them use an active RFID chip that requires energy from the charge/receive coil in the ignition switch to power the handshake chip. So you can't simply pry out the chip and use it in a new key. You have to either remove the entire circuit board (which has a separate charge circuit for the RFID chip) OR have the new key's RFID programmed for the car. Dealerships will not program an aftermarket key for you. They will only order a new pre-programmed key from bmw. Which is why they charge about $250 for a new key. Alternatively you can purchase a car key programmer from China that can program the new key and control module in the car. This is the only option for getting an aftermarket key to work unless you swap over the entire circuit board from your old key (which isn't usually an option because the reason for a new key purchase is to replace a key with a defective circuit board).

I hope that answers your question?

Last edited by Q4; 08-11-2019 at 12:50 AM.
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