1997 Bonneville, Code 0751

Hello,
I am new to posting on here, i have looked on this great site a few times.

Got a 1997 Bonneville, 3800, Se, with a code 0751. The transmission will start out like in 2nd, and does not shift. The scanner code was this 0751. They tell me that there is a sensor in a side cover of the transmission. What are your thoughts? thanks

Solenoid not sensor, do a site or google search for the info.