We have done a lot of GM flashing, not our first rodeo. Using a Passthrough, and SDS. First, on this 08 Silverado 2500HD, we replaced SDM for Air Bag light, and flashed it, out the door. That lasted a week. Back with light on, SDM seems dead. Also saw some wierd WF on Alt, and replaced it. Replace SDM, and front impact sensor, and started flashing again. No Comm to new SDM. Full Comm testing shows all other modules alive on this CAN line. And, we put the SDM right into the ALDL, by itself. No Comm. Tested powers, grounds, all else thoroughly. Definition of insanity!! I really doubt that the SDM is bad. Checked with GM, part # is correct one for SDM. Next call is to TIS.

Thomas Richardson
Owner/Technician
Master Tech Automotive
Richland, Washington, USA