WARNING: This page is about a different car, the 2005 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: ECM Power, Ground, Serial Data, and MIL Schematics
Courtesy of GENERAL MOTORS CORP.
Fig 2: Engine Data Sensors - 5-Volt Reference Bus Schematics
Courtesy of GENERAL MOTORS CORP.
Fig 3: Engine Data Sensors - Low Reference Bus Schematics