Special tools required:

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61 3 300

Necessary preliminary tasks:

Remove upper section of steering column trim. See STEERING COLUMN UPPER TRIM
E46 only: Remove lower section of steering column trim. See STEERING COLUMN LOWER TRIM

Slide in special tool 61 3 300 with flattened end (A) facing ring antenna and lever out ring antenna.

Fig 1: Removing & Installing/Replacing Ring Antenna Of Electronic Immobilizer

Courtesy of BMW OF NORTH AMERICA, INC.