GMC 2007 Sierra - Manual (Page 294)

Radio Messages
CAL (Calibrated): The audio system has been
calibrated for your vehicle from the factory. If CAL
appears on the display it means that the radio
has not been configured properly for your vehicle
and must be returned to your dealer for service.
LOC (Locked): This message is displayed when
the THEFTLOCK
® system has locked up. Take
the vehicle to your dealer for service.
If any error occurs repeatedly or if an error cannot
be corrected, contact your dealer.
Radio with CD
If your vehicle has the Bose ® audio system, your
vehicle will have six Bose ® amplified speakers.
Base Radio Shown, Bose ® Similar
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