Ready is echo complete, whereas Checking is host dependency is waiting.
TCM, ECM, etc. still need to go through further cycles to finish verification.
DIM, AUM, SRS, etc. are checked without driving or further data exchange.
The TCM, for example, will do solenoid checks, geartronic circuit grounding checks,etc., but inorder to determine gear pressure, vpm feedback, and so on, it must be driven.