REDUCED BRAKE POWER Message
WARNING: This page does not describe the selected car, but rather 12 other vehicles, including the 2003 GMC Yukon XL, 2003 GMC Yukon, 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, and 2003 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.
The REDUCED BRAKE POWER message is displayed when the supplemental brake assist signal circuit is held low. This happens when the SBA is active and maintaining reduced brake power levels.