Thanks, for clarifying the scope of the AL519 being limited to emissions-related codes. I worded my post poorly and should have said the I/M button "indicates" number of codes present.
On my car, here is what comes up when I open OBDII/EOBD:
Control Module
$07E8
$07E9
Then, when I open each one for ID info:
$07E8 CAN STD FAST - ECU Name ECM-EngineControl
$07E9 CAN STD FAST - ECU Name TCM-TransmisCtrl
So, will the I/M button indicate how many codes are present from both of these, ie all DTCs total without having to open and view each one separately just to see if there are any codes present?