I have a 2000 S-10 Blazer (Trail Blazer Model) with the Auto 4WD option. I am getting the 1875 (4WD Low Electrical Circuit Fault). The truck hits 4th gear by 10mph. I know that a false signal is being sent and making the truck think it is in 4WD Low when it is not thus the transmission is shifting like it is in 4WD Low when it is not.
I have cleaned the green corrosion on the large orange plug that is plugged into the TCCM and this has not helped the shifting issue. I unplugged the same orange plug from the TCCM and the truck now shifts fine and properly but of course I have no 4WD. The question is this...in the experience of those on this forum, what is usually the prob, the TCCM or the Encoder Motor. Any ideas or guidence will be useful.

 

Have a look at this:
P1875 - 4 Wheel Drive Low Switch Circuit