GM Service Manual Online
For 1990-2009 cars only

Class II Serial Data Link

The Class  II serial data link allows these modules to communicate data with each other:

    • Body Control Module (BCM).
    • Electronic Brake Traction Control Module (EBTCM).
    • Heater-AC control (if equipped with RPO CJ2).
    • Instrument cluster.
    • Powertrain Control Module (PCM).

In addition, the Class II serial data link allows a scan tool to communicate with these modules for diagnostic and testing purposes. The Class II serial data link is located at the DLC connector terminal 2, which consists of circuits 1036, 1037, 1038, 1049, 1122, and 1132.

UART Serial Data Link

The UART serial data link allows a scan tool to communicate with the Supplemental Inflatable Restraint (SIR) Sensing and Diagnostic Module (SDM) for diagnostic and testing purposes. The UART serial data link is located at the DLC connector terminal 9, circuit 800.

Entertainment and Comfort (E&C) Serial Data Link

The Entertainment and Comfort (E&C) serial data link allows a scan tool to communicate with the radio and CD player (if equipped with RPO U1S) for diagnostic and testing purposes. In addition, the E&C serial data link allows the radio and the CD player (if equipped with RPO U1S) to communicate data with each other. The E&C serial data link is located at the DLC connector terminal 14, circuit 835.