That's not good. The voltage reading in the Pro M software should be steady and match or be ever so slightly lower than the voltage measured directly at the battery.The voltage at my battery with the ignition on is a steady 12.2v. On the laptop it’s not steady at all it bounces anywhere from 10v-11.85v. It tends to be in the mid 11v range but like I said it’s not steady it just bounces all over the place. Once I turn the ignition off I see the voltage goes up to somewhere in the low 12v but still not steady.
I tried installing a fairly newer battery from one of my other cars and still had the same problem. I think I might have wiring issues, it’s just weird that sometimes it works and sometimes it doesn’t. Where does the pro-m gets its voltage reading from? I can start by checking there.
I was reading on a website that Ford ecm need to see 18v to be able to do any programming, I wonder if the pro-m is set up the same way.
The Pro M EFI harness has a relay for ECU power in the kickpanel. I'd start by looking at that. Make sure the wires are securely in there. It's possible that one came loose when pulling everything through the firewall.