A testing method for an electric motor for an actuator of an internal combustion engine provided with a pinion (3*); wherein the electric motor is tested during a step of installing said actuator of the internal combustion engine in which the pinion (3*) of the electric motor itself is free to rotate without any mechanical load; the method comprises the steps of: controlling the supply of a voltage impulse of predetermined duration and amplitude, which is variable as a function of the features of the electric motor to be tested, to said electric motor; calculating the actual stop time (Δt stop) of the electric motor at the end of the step of controlling the supply of a voltage impulse with a predetermined duration and amplitude to the electric motor; and diagnosing the presence of faults in the electric motor as a function of the actual stop time (Δt stop) of the electric motor at the end of the step of supplying a voltage impulse with a predetermined duration and amplitude to the electric motor; the testing method is characterized in that it comprises the further steps of: determining an acceptability limit value of the stop time of the motor in a preliminary step of setting and adjusting; comparing the acceptability limit value of the stop time with the actual stop time (Δt stop) of the electric motor at the end of the step of controlling the supply of a voltage impulse with a predetermined duration and amplitude to the electric motor; and diagnosing the presence of faults in the electric motor as a function of the comparison of the acceptability limit value of the stop time of the actual stop time (Δt stop) of the electric motor at the end of the step of controlling the supply of a voltage impulse with a predetermined duration and amplitude to the electric motor. controlling the supply of a voltage impulse of predetermined duration and amplitude, which is variable as a function of the features of the electric motor to be tested, to said electric motor; calculating the actual stop time (Δt stop) of the electric motor at the end of the step of controlling the supply of a voltage impulse with a predetermined duration and amplitude to the electric motor; and diagnosing the presence of faults in the electric motor as a function of the actual stop time (Δt stop) of the electric motor at the end of the step of supplying a voltage impulse with a predetermined duration and amplitude to the electric motor; the testing method is characterized in that it comprises the further steps of: determining an acceptability limit value of the stop time of the motor in a preliminary step of setting and adjusting; comparing the acceptability limit value of the stop time with the actual stop time (Δt stop) of the electric motor at the end of the step of controlling the supply of a voltage impulse with a predetermined duration and amplitude to the electric motor; and diagnosing the presence of faults in the electric motor as a function of the comparison of the acceptability limit value of the stop time of the actual stop time (Δt stop) of the electric motor at the end of the step of controlling the supply of a voltage impulse with a predetermined duration and amplitude to the electric motor. determining an acceptability limit value of the stop time of the motor in a preliminary step of setting and adjusting; comparing the acceptability limit value of the stop time with the actual stop time (Δt stop) of the electric motor at the end of the step of controlling the supply of a voltage impulse with a predetermined duration and amplitude to the electric motor; and diagnosing the presence of faults in the electric motor as a function of the comparison of the acceptability limit value of the stop time of the actual stop time (Δt stop) of the electric motor at the end of the step of controlling the supply of a voltage impulse with a predetermined duration and amplitude to the electric motor.