It's likely on a sticker on the module itself and possibly in your manual.

It is not 0000 (or at least that's highly unlikely).

Q: How do you get a new Bluetooth passkey card?

A: The BT passkey is printed on a laminated card that is part of the on board literature. This
card should be retained for the customer’s future reference. The BT passkey is also printed on
the Telematics Control Unit (TCU) label. A diagnostics job will be available on the next DIS CD
to be released in March 2005 (DIS 40.xx or 41) to read this information.
Before then, if the passkey is lost, the TCU should be removed and the BT passkey read from
the label. No TCU’s should be replaced or warranted for problems arising from a lost BT
passkey card. A replacement card is not available.
BT passkeys are used on 3 Series, X3, X5 and Z4 models. Because of the two-way pairing
process used in the 5 and 6 Series vehicles, they do not require a BT passkey. Model year ’06, 7
series will require a BT passkey.