Have you managed to command the motor to move to particular position or just used a potentiometer instead of the encoder to get a voltage range identified as "2 Lo" ?
As another way of getting 2 Lo, I think it iwould be possible to make a module that will command the axle actuator to disengage the right wheel in 4 Lo on demand, without letting the TCCM know about that.
The idea of circumventing the front axle disconnect circuitry seems like a fairly easy thing to do with a switch and/or relay to break the control line from TCCM to the front axle disconnect actuator while maintaining the disconnects status switch signal.
As a proof of concept sort of thing I did manage to position the encoder/motor to the 2 Low signal position as previously identified by a Tech 2 and drove around a little to confirm I had rear wheel drive only and low range as well. The process had a low success rate achieving the goal twice in 8 or 10 attempts. And even with a successful transition to 2 Low I set an encoder malfunction code of C0327.
What I did was to connect a particular resistance between the encoder signal to the TCCM and the low reference. This parallel resistance drops the signal voltage that the TCCM sees and uses to position the shift motor. Thus the signal then seen by the TCCM would be offset from the true shift motor position. I wanted to have the encoder signal at the TCCM read in the 4 Low range of 0.49 to 0.80 vdc while the encoders actual unmolested signal voltage was at the 2 Low range of 0.82 to 1.24 vdc, ideally favoring the lower end for more engagement of the low range gearing.
I connected the added resistance during a shift from 2 High to 4 Low. I tried to time the connection to when I heard the shift motor in motion. I could hear the shift motor jockeying around a bit. And the C0327 code sets pretty quickly, possibly even immediately upon the added resistance connection. I suspect the code sets as a result of the abrupt change in encoder signal voltage seen by the TCCM.
On the two 'successful' attempts I read 1.14 vdc and 0.98 vdc at the signal line to the TCCM. I don't know if the TCCM actually positioned the shift motor there or not. The dash display would display 4 Low and the only indication something was not 'factory correct' was the Service 4WD light.
I do NOT advise anyone to attempt this !! In my case it is a second vehicle and available for such shenanigans. On the failed attempts I ended up in 4 Low normally and at least once the Transfer Case slipped out of my intended position and grinding gears were heard as it was between engagement and neutral. Sometimes I would drive about 50 yards or so and then slip into neutral.