2006 Trailblazer disabling shift from 1st gear to 2nd

[MaxEcu]

hello,

I am trying wothout success to figure how to disable a gear shift from 1st to 2nd in P12 2006 Trailblazer in 4x4 LOW mode only
I have the next method : Transmission > Shift pressure > Upshift > General > Base shift pressure Vs. Torque Vs. Gear - Normal brake / pwron
and also Transmission > Shift pressure > Upshift > General > Base shift pressure Vs. Torque Vs. Gear - Performance brake / pwron

Any suggestions here?

thanks to all

[blindsquirrel]

I believe the 1-2 'safety shift' with selector in D1 is a function of the valve body, not the ECM/TCM. 4L60Es will turn to shrapnel if overreved in 1st gear.