In order to configure the Native Instruments Kontrol S4 for use with Torq 2.0 you must load the 3rd party configure file "TraktorKontrolS4Config.ncc" to the Kontrol S4.  This file is located:

    Macintosh HD>Applications>Avid>Torq>3rdPartyConfigurationFiles (Mac)
    C:\Program Files (x86)\Avid\Torq 2\3rdPartyConfigurationFiles (Vista 64 & Win7 64)
    C:\Program Files\Avid\Torq 2\3rdPartyConfigurationFiles (XP, Vista 32, Win 7 32)

Please consult the Kontrol S4 documentation on how to load/configure ncc files.