I have a 2005 Trailblazer EXT V8 with 80,000 miles on it. Without any prior 4WD issues, my service 4WD came on. When I tried to select anything other than 2WD the switch just blinks and I can hear it trying to engage then kicking back out. I took it to the dealer with the diagnosis of TCCM. Replaced that and had it programmed, still no 4WD. The dealer then said since there was previously no power to the TCCM it only gave that code. Now that the TCCM has power it is indicating the actuator needs to be replaced. After replacing the actuator myself still no change in the 4WD condition. I am sick of wasting my time at the dealer hooked up their computer and still no fix. Any suggestions?