I'm thinking ths is your issue:
Subject: ABS Red Brake SVC And 4WD Light On HVAC Blower Inoperative - keywords B1375 C0379 DTC HI4 ignition IPC L04 MIL on U1000 U1041 PIT3832C (12/04/2007)Models: 2004-2007 Buick Rainier, 2002-2008 Chevrolet Trailblazer models, 2002-2008 GMC Envoy models, 2002-2004 Oldsmobile BravadaThis PI was superseded to update Recommendation/Instructions and model years. Please discard PIT3832B.The following diagnosis might be helpful if the vehicle exhibits the symptom(s).Condition/Concern: Vehicle may exhibit a combination or all of the following symptoms: ABS light on, Red BRAKE light on, Service 4WD light on, HVAC blower motor inoperative. Various DTCs may also be present.Recommendation/Instructions: Diagnose for loss of battery voltage to the rear fuse block on circuit 300 ORN for the following fuses:Note: Prior to proceeding forward with the information below, it is important to verify the voltage as indicated however it is equally important to verify the integrity of each circuit. This can be achieved by performing a voltage drop test or by adding a device to each circuit that will supply sufficient load to verify the circuits integrity.HVAC 30A, 4WD 15A, HVAC 1 10A, BRAKE 10A, TBC RUN 3A.