Power probe IV driver test mode. How useful is it?

Power probe says: Modern ECUs have circuits that let the ECU know if a component is actually plugged in.

Has anyone encountered a ecu that needed voltage on the control circuit before it would activate it?

Last week.
05 Cobalt, codes for 1-2 shift solenoid. Checked operation of the driver with scan tool and test light, nothing. Confirmed results by testing 3-4 solenoid.
Measured current draw of 1-2 solenoid with computer disconnected, 10 amps!
So it needs a computer and a shift solenoid.
After repair of trans and computer replacement, immediate TCC fault codes that will not clear.
So I connected the PP4 to the control wire for the TCC solenoid in "driver test mode", cleared the codes and they stayed gone. Activated the driver with the scan tool to prove the problem was with the solenoid in the trans, not the new/used computer.

I broke the solenoid reinstalling the side cover and had to go back in...