DTC P0700: Transmission Control System (Mil Request): Description
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2003 GMC Yukon XL, 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Suburban, and 2003 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The Malfunction Indicator Lamp (MIL) requests circuit signals the Engine Control Module (ECM) that the Transmission Control Module (TCM) is requesting MIL illumination.