In the Archives you will find a nice description of the procedure under "Electrical". The first post under Spine models explains how to dial in the TPS using a volt meter. I used to probe the connector at the TPS end with a straightened paper clip (de-burr the end so it does not cut the rubber seal), and you have to poke it in quite a way to get contact.
I think the wire closest to the throttle body gives the reading you want.
I'm not sure the 5AM software will read the 15M. I have the pro version of software so I haven't tried this. As to reading with a volt meter, I pull back the rubber boot and back probe the two outside wires as those are the ones the 15M and P8 systems use. I only back probe now to re-establish the 150 mV baseline reading for the butterfly completely closed.