You need to get the radio's serial number. A BMW parts counter should be able to match up your serial number with the security code. There are two types of security codes, a EURO one and a US one. Get BOTH of them, because some radios are coded with the EURO code even though it's a US unit. There are two ways to get the serial number:
1) Enter programming mode and get the serial number. This is done by turning off the radio, Turn on the radio then, hold down the M button on the left lower portion of the radio's faceplate for about 10 seconds. The display will change to the radio's serial number. Write this down. Should be a 8 digit number.2) pull the radio out, on the sticker should be the serial number. It is the 8 digit number that follows the BP0273. You can see what i'm talking about in the pictures of the radio unit i just sold: Pictures of Radio
I hope that helps...
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