Method for diagnosing a speed/position sensor

A method for diagnosing a speed sensor or a position sensor of an internal combustion engine, the speed sensor or the position sensor including a toothed wheel, which rotates as one with a shaft, and a matter detector, which is configured to be fixed opposite the toothed wheel and controls a base of a transistor, the method comprising:

• detecting a short circuit between an output of the speed sensor or the position sensor and one of:
• (i) a power supply of the speed sensor or the position sensor, and (ii) another power supply;
• testing for excess current consumption by the power supply of the speed sensor or the position sensor when the transistor is activated;
• and
• determining that the short circuit is between the power supply of the speed sensor or the position sensor and the output of the speed sensor or the position sensor, when the test is positive, and determining that the short circuit is between the other power supply and the output of the speed sensor or the position sensor, when the test is negative.