Hello and welcome to Just answer.com, Super mechanic here. About your vehicle.
There has been a service bulletin for that type of concern. Here is what it states.
Bulletin No.: 05-08-05-008
Date: August 18, 2005
Intermittent Heated Seats Inoperative, DTC B3941 Set (Reprogram Driver Seat Module) Models:
2003-2005 Cadillac Escalade, Escalade ESV, Escalade EXT
2003-2005 Chevrolet Avalanche, Silverado, Suburban, Tahoe
2003-2005 GMC Sierra, Yukon, Yukon XL, Yukon Denali
All with Seat FRT, Individual (Non BKT) (RPO AN3)
2003-2005 HUMMER H2 with Seat, Front Bucket Deluxe (RPO AR9)
Some customers may comment that occasionally the seat heater will not operate when activated. If the ignition key is cycled OFF and back ON again, the heated seat will operate correctly. Also, on some LB7 diesel engine vehicles, the seat heater may turn itself off during the first 10 minutes of operation. This occurs only with the first activation for the day and works correctly with subsequent activations immediately after the event. These conditions are intermiffent and DTC B3941 may be set.
Technicians are to reprogram the driver seat module with an updated software calibration. This new service calibration was released with TIS satellite data update version 6.5 available June 13, 2005. As always, make sure your Tech 2(R) is updated with the latest software version.