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.

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 the SDGM is not activated due to an open wake up circuit from the BCM, the SDGM will not energize the wake up signal circuit to the BECM when it should and the HPCM will set DTC U1812
Different DTCs may set in different modules along with this DTC depending on where the fault occurs and the vehicle operating conditions when the fault occurs.