I am bringing back an old post since I am having the same problem.  Only when I ground the K terminal nothing happens except it delays the INFL REST light coming on by a few seconds.  If I don't ground it, the light comes on immediately when the key is switched to on, thus I am sure I have a good ground.  1990, 6 speed, stock.  Replacement radio. 
Thanks in advance for any help. 
Ken