Scan Tool Does Not Communicate With Class 2 Device

SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE

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. Connecting a scan tool to the data link connector (DLC) allows communication with the modules for diagnostic purposes. DTCs may be set due to this symptom and during this diagnostic procedure. Complete the diagnostic procedure in order to ensure all the DTCs are diagnosed and cleared from memory.

TEST DESCRIPTION

Steps 1 - 10:

The numbers below refer to the step numbers on the diagnostic table.
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.
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(R)), 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
7. Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
9. A poor connection at splice pack SP205 will cause this condition but will not set a DTC.
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.