And what more simple and reliable way to do that than to initiate the command to drive the motor to stall stop one more time? Which is exactly what it does.
As an electrical engineer I had a blast reading this thread. But what a rollercoaster of emotions when scope traces were posted, but the ones we really wanted to see never materialised!
I still wonder what was behind the talk of the differing sensor signals? It did suggest that maybe some clamping force feedback signal is derived within the controller and potentially used to stop the motor at a certain force. Normal park mode triggering at 1.7 V, but 'superpark' mode triggering at 4.5 V, i.e. higher clamping force.
But I have no idea. Seems more likely they would be the same and the push and hold 'superpark' is simply the manual input complying with e-brake/handbrake system regs. The only mode of operation I'd expect to have some intelligence and variable behavior is operation while the car is moving.
That said, I'm also very much a mechanical engineer into mechanical testing and this would be my preferred way to determine for sure! All we need is a friction modifier to bring the force required to defeat the brakes into easily measurable range! Is anyone volunteering to oil their brakes?
3D print some grooved nylon brake pads?
If only we had a drum-based handbrake mechanism like many of my older cars - it'd be so weak we could do this test easily without such modifications!