Transfer Case Shift Control Module
WARNING: This page is about a different car, the 2004 GMC Yukon XL and 2004 GMC Yukon. However, it is still accessible from the selected car via links, so may be relevant.
Courtesy of GENERAL MOTORS CORP.
The transfer case shift control module monitors vehicle speed via the Class 2 date bus from the powertrain control module as well as controlling the operation of the transfer case encoder motor assembly.