This GM TSB refers to the 2009 Buick Lucerne Super (with 18-inch wheels) and the 2009 Cadillac DTS. The issue involves brake noise and/or pulsation, and information regarding the FNC (Ferritic Nitro-Carburizing) brake rotors.
Part numbers covered include front rotor 25980048 and rear rotor 25982106.
Beginning with the 2009 Cadillac DTS, GM introduced a new brake rotor technology called Ferritic Nitro-Carburizing (FNC). This is an additional step in the manufacturing process that creates a hardened outer layer on the surface of the rotor, which is intended to reduce rotor rusting, and extends rotor life (wear).
Since this new technology protects against excessive rotor corrosion, it not only looks better through open-spoke type wheels, but it also helps to reduce thickness variation which creates pulsation.
PARTS RESTRICTION PROCEDURE
DO NOT TURN (re-surface) these rotors. Due to the implementation of the FNC technology, the rotor should be replaced.