Crankshaft, transmission or camshaft sensor, diagnosis system and method implementing such a sensor
The invention relates to a crankshaft, transmission or camshaft sensor ( 10 ) for a motor vehicle, intended for being connected to an engine control unit ( 30 ) by a cable ( 20 ). The sensor comprises a processing module ( 17 ) and a voltage-modifying circuit ( 18 ) configured to generate an output signal via an output port ( 12 ) of the sensor ( 10 ) allowing a diagnosis module ( 36 ) of the engine control unit ( 30 ) to detect and identify faults of the sensor ( 10 ) or the cable ( 20 ). In particular, the processing module ( 17 ) is configured to provide on its output port ( 172 ), when the toothed target ( 14 ) is immobile, a predetermined pattern representing the fact that the toothed target ( 14 ) is immobile, this predetermined pattern corresponding to a status change of the output port ( 172 ) of the processing module ( 17 ) with a predetermined time and repeated periodically. The invention likewise relates to a diagnosis system ( 1 ) comprising such a sensor ( 10 ), a cable ( 20 ) and an engine control unit ( 30 ). The invention also relates to a diagnosis method ( 50 ) implemented by said diagnosis system ( 1 ).
1. A crankshaft, transmission or camshaft sensor for a motor vehicle for connection to an engine control unit of the motor vehicle, said sensor comprising:
a toothed target,
a measurement cell suitable for delivering a raw signal that is representative of the variations in a magnetic field that are induced by the rotation of the target, and
a processing module suitable for placing an output port of the processing module, according to the raw signal, in a first state or in a second state, the transitions between said first state and said second state being representative of instants in time at which teeth of the target pass the measurement cell,
an electronic voltage modifier circuit arranged between the output port of the processing module and an output port of the sensor, said voltage modifier circuit being configured to deliver, over the output port of the sensor, an output signal that is equal to a potential V H when the output port of the processing module is in the first state, and to a potential V L when the output port of the processing module is in the second state, said potentials V H and V L differing from one another and differing from a supply potential V S of the sensor and from a ground potential V G ,
wherein the processing module is further configured to deliver, over the output port of said processing module, when the toothed target is immobile, a predetermined pattern that is representative of the fact that the toothed target is immobile, said predetermined pattern corresponding to a change of state of the output port of the processing module with a predetermined duration and repeated periodically.
2. The sensor as claimed in claim 1 , wherein the predetermined pattern takes the form of a pulse pair, each pulse corresponding to a change of state of the output port, with a predetermined duration.
3. The sensor as claimed in claim 2 , wherein the durations at the potential V H or at the potential V L differ from one another, and also differ between the two pulses of the pulse pair.
4. The sensor as claimed in claim 1 , wherein the voltage modifier circuit includes a resistor placed between a power supply port of the sensor and the output port of the sensor, a resistor placed between an output port of the processing module and the output port of the sensor, and a resistor placed between a ground port of the sensor and the output port of the sensor.
5. The sensor as claimed in claim 1 , wherein the electronic voltage modifier circuit includes only passive discrete electronic components.
6. A diagnostic system comprising:
a sensor as claimed claim 1 ;
an electrical cable including a power supply wire, a ground wire and a signal wire; and
an engine control unit connected to the sensor by the cable and including:
a power supply port connected to a power supply port of the sensor by the power supply wire;
a ground port connected to a ground port of the sensor by the ground wire;
an input port connected to the output port of the sensor by the signal wire; and
a diagnostic module connected to said input port, said diagnostic module being configured to detect and to identify, according to a signal observed on the input port of the engine control unit, a fault in the sensor or a fault in the cable.
7. The system as claimed in claim 6 , wherein the input port is also connected to a pull-down resistor which is connected to a ground line of the engine control unit.
8. A motor vehicle including a system as claimed in claim 6 .
9. A diagnostic method implemented by a system as claimed in claim 6 , comprising:
a recurring step of the diagnostic module retrieving values taken by the signal observed on the input port of the engine control unit;
a step of the diagnostic module comparing the values taken by said observed signal with respect to predefined expected values;
a step of the diagnostic module detecting and identifying, according to the differences between the values taken by said observed signal and the predefined expected values, a fault in the sensor or a fault in the cable.
10. A diagnostic method implemented by a system as claimed in claim 7 , comprising:
a recurring step of the diagnostic module retrieving values taken by the signal observed on the input port of the engine control unit;
a step of the diagnostic module comparing the values taken by said observed signal with respect to predefined expected values;
a step of the diagnostic module detecting and identifying, according to the differences between the values taken by said observed signal and the predefined expected values, a fault in the sensor or a fault in the cable.
11. A motor vehicle including a system as claimed in claim 7 .