I do hope you see why the voltage divider won't work.
If the pin is intended to be pulled to 0 volts, you may
not get that close.
With 1ma source, 2K will be at 2V at the top. This may
be enough to partially turn on the transistor to the
motor, when it should be off.
When the Arduino pulls down, there well be 1V at the
top of the divider. Again, that may not be enough to
properly turn on the drive, causing more power loss
in the drive transistor.
Not knowing the circuit of the drive the divider is clearly
a bad idea.
Now, you connect 12V. Again, not knowing the circuit
attached, the 2:1 divider could be putting 6V on the
Arduino.
Dwight