Just a quick note : I was getting the "service 4 wheel drive" indication every time I started my 2004 H2 - I was worried that one day the transfer case motor would quit completely so I purchased a Dorman Transfer Case Motor #600-908 but it did not function correctly ( you have to change out and move the connector pins and I did not want to hassle with that )

I ended up purchasing this : ACDelco 89059688 GM Original Equipment Transfer Case Four Wheel Drive Actuator with Encoder Motor off Amazon for $218 and in less than 45 minutes my problem is solved!

Spend the extra $ for the original equipment actuator and if you have put the TC in neutral and the TC shaft does not match the new TC encoder motor just use a crescent wrench to move the TC shaft to match what the motor is set at.

No more codes, Hummer shifting perfectly !!!

 

Mine would crap out any time the temp went below about 35º but would come back after the drivetrain was thoroughly warmed up. Went the same route as you, no problems since.

 

 

Your lucky you went that route, most Dorman products are cheap crap.