An automatic calibration method for a motor vehicle camshaft sensor, the vehicle having at least one camshaft, a toothed encoded target (or magnetic encoder) associated with this camshaft, and a magnetic field sensor placed near the target to detect magnetic field variations caused by the passage of the teeth of the target near the sensor, the sensor delivering signals corrected by a predetermined detection threshold K, the method including: continuously measuring the value of the magnetic field during at least one revolution of the target, determining the maximum amplitude Amax of the field measured during this revolution, determining the minimum amplitude Amin of the field measured during this revolution, finding the ratio of the amplitudes A min A max and determining an auto-adaptive correction coefficient K′ to be applied to the signal received from the magnetic sensor, with allowance for the geometrical imperfections of the target, according to the following formula: K ′ = A min A max × K .