Diagnostic Aids

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2008 GMC Yukon XL, 2008 GMC Yukon, 2008 Chevrolet Tahoe, 2008 Chevrolet Suburban, and 2008 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

Use the DTC Descriptor list above to determine the module which is not communicating.
Use the Hybrid High Voltage Module Chart to determine if a specific module is a high voltage module.
Use Data Link References to determine which serial data communication system a specific module uses.
When testing circuits to the SDGM access can be accomplished by removing the instrument panel center trim panel. Note that this procedure does not allow removal of the SDGM, only access to the connector. Refer to Instrument Panel Center Trim Panel Replacement (Cadillac) or Instrument Panel Center Trim Panel Replacement (Except Cadillac) .
If there are multiple non-communicating modules or loss of communication DTCs, choose the one closest to the data link connector (DLC) to begin diagnostics.
Some modules may not have internal protection for specific voltage outputs and may open a battery positive voltage or ignition voltage source fuse. If a voltage input fuse is open and no short is found in that circuit, ensure that no module output voltage circuit is shorted to ground before replacing the module.
This diagnostic can be used for any module that should communicate with high or low speed GMLAN serial data providing the vehicle is equipped with the option that uses that module.