how to turn on thx amp in '06 navigator

My 2006 Navigator has the factory THX navigation system and I can't find any info on how to turn on the factory amp other than it cant be done with a 12V remote wire.   I've reviewed the wiring diagrams (factory manuals) and the only 2 pins which are connected in the amp but which don't receive audio signals or output to the speakers are in connector C2291a.  Pin 9 is GY/BK "Clip Detect" and Pin 22 is DG/VT "Enable/Clip detect" and they must be involved in turn on/off in some way, but can't find any detail.  The only relevant pinpoint test is used if there is a loud popping when cycling the ignition switch.  It says to turn ignition on and head-unit off and look for a voltage on pin 22 - any voltage there idicates a bad circuit in need of repair - No voltage there means the amp needs to be removed and sent to repair facility.  

 I understand that later 2007+ THX amps are turned on with CAN signals which you can get from AFDI-THX-01, and I've read some earlier amps are turned on with a 5V signal you can get from AFDI-5V.  Does anyone know for sure how to turn on/off the THX amp is turned on/off?  I'd like to know the best approach before I take it apart.   If I don't get an answer I suppose I can test for 5V once I have it apart.