GM Service Manual Online
For 1990-2009 cars only

Class 2 Serial Data

The Class 2 serial data link allows modules to transmit, receive, or exchange data:

    • electronic climate control module (ECCM)
    • transfer case shift control module (TCSCM)
    • electronic brake control module (EBCM)
    • powertrain control module (PCM)
    • vehicle interface unit (VIU)
    • body control module (BCM)
    • instrument panel cluster (IPC)
    • driver information center (DIC)
    • memory seat module (MSM)
    • inflatable restraint sensing and diagnostic module (SDM)

Circuit Description

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. In addition to this, Node Alive messages are transmitted by each module on the class 2 serial data circuit about once every 2 seconds. When the module detects the class 2 serial data circuit shorted, the setting of all other class 2 serial communication DTCs is inhibited and a U1300, U1301, or a U1305 DTC will set.