DTC P0719: Brake Switch Circuit - Low Input (4L80-E Transmission): Description
WARNING: This page does not describe the selected car, but rather 11 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Yukon, 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, and 2002 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.
The TCC/Stoplamp switch indicates the brake pedal status. The normally-closed TCC/Stoplamp switch supplies a battery voltage signal to the Powertrain Control Module (PCM). The signal voltage circuit opens when the brake pedal is applied. If the PCM detects an open TCC/Stoplamp switch circuit during accelerations, then DTC P0719 sets.