12ohms is just a nominal resistance.

I get your chart. We can't start with more than 12 volts. So, Vb is fixed. If R is a transistor or solenoid driver. The ECU can ramp the R down at any speed it wants but with a fixed Vb and fixed L it's the only variable in the circuit. Our L also has an R component too, unlike a typical small inductor. Which limits current as well.

We know the output can measure current though so, maybe they are looking for a current ramp that ID's the Solenoid. I was thinking they were detecting the collapse of the magnetic field but measuring the inrush current ramp makes more sense

A solenoid has enough wraps of wire on it to have a DC resistance that in the case of Solenoid A is about 12 ohms. The shop manual indicates the ECU will set a CEL if the resistance of the solenoid if less than 8 ohms or greater than 100K ohms. So, I believe if you use a typical inductor like you'd buy at Radio Shack with effectively zero resistance, you'll end up with a code. It'll draw too much current.

I haven't dug too deep yet. I basically have 2 data points.

1 - With a 12 ohm power resister, solenoid A sets a code.

2 - With solenoid A plugged in (nominally with a 12 ohm DC resistance) , there's no code.