Diagnostic Aids

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2012 GMC Yukon XL, 2012 GMC Yukon, 2012 Chevrolet Tahoe, 2012 Chevrolet Suburban, and 2012 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 control module which is not communicating.
If there are multiple non-communicating control modules choose the one closest to the EBCM.