GM Service Manual Online
For 1990-2009 cars only

When the scan tool is connected to the DLC, it is powered by CKT 840 (ORN) through pin 16. The scan tool is grounded through CKT 750 (BLK). Splice Pack 261 (SP261) busses all of the data lines together to allow communication with the following components through CKT 1132 (PPL) cavity 2:

    • The Vehicle Control Module CKT 1049 (DK GRN)
    • The Body Control Module CKT 1037 (LT GRN)
    • The Inflatable Restraint Sensing Diagnostic Module CKT 1128 (DK BLU)
    • The Electronic Brake Control Module CKT 1122 (LT BLU)
    • The Automatic Transfer Case Shift Control Module CKT 1133 (DK GRN/WHT)
    • The Compass and Temperature Display Module in the Overhead Console CKT 1127 (YEL)
    • The Instrument Panel Cluster CKT 1036 (GRY)

You can then monitor the system operations for diagnostic purposes.

Pin 5 CKT 550 (BLK) is a ground return for the Class 2 data signal.