Typically there are 2 solenoids in a 4 speed Auto. Opening + closing the 2 solenoids select the 4 gears. Applying 12 volts to the proper solenoids will give you 1 gear. However you will have to turn the pump to make fluid pressure to hold the clutches . . . . . Wasteful . . .
Here's a link to the Gear Vs Solenoid position for the AE340
MK3 TSRM On-Line