You've checked behind the panel inside the left rear taillight, and no silver box is mounted there? Not all cars had ULF. Some had what we call a TCU, or Telematics Control Unit. In either case, the Bluetooth pass-key was printed on the label of the module. The 4 numbers next to "PK" are the passkey.

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2003 E53 3.0i
DOB 10/15/2002
Sienna red, Savannah Beige Dakota leather
Type FA53, Engine M54B30

2018 G02 30i
DOB 4/21/18
Black Sapphire Metallic / Canberra Beige Vermasca leather
Engine B46O