What is the meaning of Dhammavicaya What is the exact meaning of the second factor of Enlightenment 'Dhammavicaya'? Does it mean: enquiry of the Dhamma (buddhasasana)? Or is it the enquiry (= tilakkhana) of all dhammas i.c. all phenomena? Or both?
The sutta says:


  Abiding thus mindful, he investigates and examines that state (dhammaṃ) with wisdom and embarks upon a full inquiry into it. On whatever occasion,
  abiding thus mindful, a bhikkhu investigates and examines that state (dhammaṃ) with wisdom and embarks upon a full inquiry into it—on that occasion
  the investigation-of-states enlightenment factor is aroused in him,
  and he develops it, and by development it comes to fulfilment in him.


The word 'dhammaṃ' above is 'singular' (rather than plural). Therefore, dhammavicayasambojjhaṅgo (the investigation-of-states enlightenment factor) appears to mean examining satisambojjhaṅgo (the mindfulness enlightenment factor) with wisdom.