On page 127, you can see that “investigating consciousness” does not only perform the function of “investigating” inside a CV, but also the function of Bhavanga, which might be what we are looking for, because this is the citta that precedes the functional “Manodvara citta” inside a Minddoor process, and also it is a resultant (vipaka).
What do you think?
Page 127 should explain it.