Hi,
My car is a Fiat Uno 1.1 ie from 1992.
The stepper motor doesn't work. When I give ignition it push out itself and after it still in this position, not move. The stepper motor is good, because when I check it directly from the battery it works in both direction. If I disconnect the plug from the potentiometer of the injector during the ignition at that time the stepper motor goes back, if I connect it, it comes out. The complete injector was replaced for a new one but the situation is the same in both case. Currently the stepper motor is out of the engine and the car goes without this.

I already made ECU reset.
Could You help me?

Check cable and connectors.
Open the engine control unit main plug and look for corrosion.
"Beep" the wires or use a lamp to see if none of them are broken.