Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. 2:  A current DTC, U1300 or U1301, may be retrieved only from the engine control module (ECM), because the ECM is connected to both class 2 and high speed GMLAN buses, but it communicates with the scan tool on high speed GMLAN bus only.
2. 3:  A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit. The scan tool communicates with the following modules on the class 2 serial data circuit:
   • The body control module (BCM)
   • The communication interface module (OnStar®), w/UE1
   • The digital radio receiver (DRR), w/U2K
   • The driver door module (DDM)
   • The driver seat module (DSM), w/AAB
   • The DVD player
   • The electronic brake control module (EBCM)
   • The endgate module (EGM), for XUV
   • The HVAC control module
   • The HVAC control module - rear auxiliary
   • The inflatable restraint sensing and diagnostic module (SDM)
   • The instrument panel cluster (IPC)
   • The liftgate control module (LGM), except XUV
   • The passenger door module (PDM)
   • The power roof module (PRM), for XUV
   • The radio
   • The transfer case shift control module (TCSCM), w/4WD
   • The theft deterrent control module (VTD), w/BAE
3. 7:  Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
4. 9:  A poor connection at splice pack SP205 will cause this condition but will not set a DTC.
5. 10:  An open in the class 2 serial data circuit between the DLC and splice pack SP205 will prevent the scan tool from communicating with any module on the class 2 network. This condition will not set a DTC.