My 2005 yukon denali won't start, i've took out the battery.and tested the Starter Solenoid.. Please help i think it's a bad Connection

This answer is for a no crank. My son in law has a 2005 Denali and basically the engine would not crank today. The Ignition relay would just click and all the dash lights and headlights would go off when the key was turned to the start position. Removing the starter and thoroughly cleaning all connections and the face of the starter that touches the bell housing and the bell housing where the starter seats, with a metal brush. Reinstalled starter and the car started. The starter tested fine at Auto Zone but only when the MACHINE GROUND was used. When connecting the ground to the starter housing the starter failed. Apparently the body of the starter is the ground and has to have a clean, tight connection to the housing. We thought that the antitheft system was causing the problem as the alarm is malfunctioning (not going off when door is open and alarm on) guess this is a seperate issue and was not the cause of the inability to crank the starter. BTW, a test of the starter while attached (touching the power + on the starter to the S terminal on the starter did not produce any results. Power + off the starter to the other post spun the starter but would not engage the selenoid to extend the bendix spring to engage the flywheel. If you test the starter and nothing happens when power to S terminal and the other post when energized spins the starter motor the GROUND is to blame. Hope this helps. Not a fun thing to do but when it works you'll be happy it didn't cost anything.