Both of the attached threads were related but don't seem to offer up a clear solution. . . . The P0758 code tells me that Shift Solenoid B may have an open circuit and needs to be replaced. . . . Now I guess I need to figure out the easiest way to confirm that it is in fact a bad solenoid and figure out how or if I can replace it. I'm guessing to check if it is the solenoid I would need to pull the tranny pan off, pin-point the solenoid and test it, see if it clicks . . .
There's a FSM troubleshooting chart in the first linked thread, attached to
this post.
The code isn't a performance code, i.e., where the TCM is commanding the solenoid and where the oil pressure controlled by the solenoid isn't changing accordingly.
Also, the code is for an open circuit or short. It's not likely a mechanically-stuck solenoid; that wouldn't cause a code related to the electrical connection being open or shorted. It could be the solenoid winding is open, or the connection at the solenoid is broken, but it could also be the wiring between the TCM and the solenoid, or the ground. There's several connectors in the circuit that could have a bad contact.
Is there any sign of the flat bottom of the pan being, or ever been, pushed up?