Abstract: The invention relates to a method of detecting a reference zone formed on the periphery of a toothed disk integral with a rotary part, for the purpose of determining the angular position of said rotary part. According to this detection method, when a reference zone is expected and at the time of the detection of a tooth (n) at a time tn, on the one hand, there is defined a time window [tmin, tmax] of duration depending on the time period Tn separating the detection of the tooth (n) and the detection of the preceding tooth (n?1) and, on the other hand, the reference zone is considered present in the absence of detection of a tooth (n+1) during said time window [tmin, tmax]. Moreover, according to the invention, the duration of each time window [tmin, tmax], calculated from a measured time period Tn, is adjusted by modulating that duration by means of a correction parameter equal to ?T=Tn?Tn?1.

Abstract: Method for determining the reversal of the direction of engine rotation for internal combustion engines having a crankshaft fitted with a target wheel having teeth, one of which is a long tooth, with a unidirectional crankshaft position sensor delivering a signal used for counting teeth and with an engine management device including a processor and a model of the engine behaviour in a stalling phase, including: recording the signal and measuring each time difference between two successive edges of the signal, calculating, on the basis of the model, the time variation of the engine position from the time differences between the edges of the signal, and estimating the stopped position of the engine, wherein the model is a second-order polynomial function of time, and the position of reversal of the direction of rotation is estimated from the calculation of the peak position of this second-order polynomial function.