here you go.
Intermittent Battery Draw, Dead Battery or HVAC Odor
May 1, 2011 9:42 PM
On some 2007-2010 OUTLOOK; 2008-2011 Enclave; 2009-2011 Traverse; and 2007-2011 Acadia, Silverado, Avalanche, Suburban, Tahoe, Sierra, Yukon, Yukon Denali, and Escalade models, an intermittent no crank condition may be found due to a dead battery.
A recent Engineering study has shown that the vehicles identified above could experience a dead battery as a result of the HVAC afterblow function being turned on at the dealership (refer to Service Information document 1865501).
The afterblow calibration may cause the blower motor to operate in a series of operating cycles which, over time, may cause the battery to drain. This is more likely to occur if the vehicle is not driven long enough between ignition cycles to maintain a sufficient battery state of charge.
Until further notice, it is recommended that the afterblow feature not be enabled, to prevent the potential of a dead battery. Also disable the afterblow feature if a vehicle has an intermittent dead battery condition that cannot be duplicated.