[HummerJim]

Originally Posted by guruerror

The one and only time I got the Service 4WD it ended up being a faulty transfer case shift control switch (15127829).

15 in the diagram: http://parts.nalleygmc.com/showAssembly.aspx?ukey_assembly=392529&ukey_make=1 027&ukey_model=14605&modelYear=2005

+1
Had the exact same issue when the H2 was new. It would come on randomly and then go off, but it started staying on and Lynch replaced the switch in 2007 and not a single SERVICE4WD since then. Problem solved.