This video shows how to test the power and ground circuits for the instrument cluster in the 2004 Tahoe. You would do these tests if you had a cluster that would not turn on.
The cluster in this Tahoe had several problems. The drivers information center would switch languages and get "stuck", the drivers information center would turn on by itself with the key "off", and sometimes the cluster just wouldn't turn on at all unless it was reset by removing and reinstalling the fuse. A new (re-manufactured) cluster fixed all of these issues.
The pinouts should be same for other GM trucks and SUVs of this era (2003-2006-ish) like the silverados, suburbans, yukon, etc.
My test connector isn't available any more, here is something else that should work:
www.amazon.com/Metra-Reverse-...