Diagnostic method for an air quality measurement sensor in a vehicle passenger compartment

Abstract

The invention relates to a diagnostic method for at least one sensor (2) intended to measure a variable representative of the air quality passing through an air supply circuit (1) of a motor vehicle passenger compartment (3), comprising: a first step of measuring a first variable representative of the air quality by the sensor, the valve (6) being in a first closed or open position of the supply circuit; a second step of measuring a second variable representative of the air quality by the sensor, the valve (6) being in a second closed or open position of the supply circuit, different from the first position; a third step of calculating the difference between the second variable and the first variable to deduce a deviation; and a fourth step of comparing the deviation with a threshold value to verify whether the sensor is functioning correctly. Abstract figure: Fig. 1

Description

Title of the invention: Method for diagnosing a sensor for measuring air quality in a vehicle interior

[0001] The present invention relates to the field of managing the monitoring of the proper functioning of an air quality sensor in a motor vehicle passenger compartment.

[0002] The invention relates more particularly to a method for diagnosing a sensor intended to measure a variable representative of the quality of the air passing through an air supply circuit of a motor vehicle passenger compartment.

[0003] A motor vehicle conventionally comprises a passenger compartment supplied with air via an air supply circuit.

[0004] The supply circuit comprises an aerator, through which air from outside the motor vehicle is admitted and a first air intake duct, called "external air inlet duct", which connects the aerator to an air pulsation fan, diffusing the air into the passenger compartment.

[0005] The exterior air intake duct further comprises a filter (or several filters, depending on the level of finish of the motor vehicle), through which the admitted air passes in order to be purified.

[0006] The filtered air is conveyed through the outside air intake duct to the air pulsation fan, which draws in the filtered air and diffuses it into the passenger compartment.

[0007] The supply circuit further comprises a second air intake duct, called the “passenger compartment duct”, forming a loop between the passenger compartment of the motor vehicle and the exterior air intake duct.

[0008] The outside air inlet duct may further comprise one or more sensors responsible for taking measurements representative of the quality of the air passing through the outside air inlet duct.

[0009] Document FR3076491B1 describes, for example, a method for determining the level of at least one pollutant in the air inside and outside the passenger compartment of a motor vehicle. The vehicle comprises a sensor adapted to determine the level of at least one pollutant in the air inside the passenger compartment of the vehicle, and an air management system adapted to ventilate outside air inside the passenger compartment. The level of the pollutant in the outside air is determined from the determined quantity of renewed air and the variation between the first and second values ​​of the measured level of the pollutant in the inside air.

[0010] However, this type of sensor can malfunction and lead to false measured pollutant level values ​​without the user noticing it immediately. The opening The outside air intake duct can be operated even though the outside air is very polluted, posing a health risk to the vehicle occupants.

[0011] It is therefore necessary to be able to control the correct functioning of the sensor but the state of the art does not disclose a procedure for monitoring the correct functioning of the sensor. The malfunction of the sensor is often detected during vehicle maintenance and this detection can take time.

[0012] The aim of the invention is therefore to overcome the drawbacks of the prior art by proposing a method for diagnosing a sensor intended to measure a variable representative of the quality of the air passing through an air supply circuit of a motor vehicle passenger compartment, making it possible to easily and quickly detect a faulty sensor.

[0013] To this end, the invention thus relates, in its broadest sense, to a method for diagnosing at least one sensor intended to measure a variable representative of the quality of the air passing through an air supply circuit of a motor vehicle passenger compartment. The supply circuit comprises an outside air supply duct connecting the interior to the exterior of the passenger compartment. The outside air supply duct comprises a filtration device and an air flow control valve positioned downstream of the filtration device and intended to close or open the outside air supply duct. The sensor is positioned in the outside air supply duct, downstream of the valve.

[0014] According to the invention, the method comprises: - a first step of measuring a first variable representative of the air quality by the sensor, the valve being in a first position of closing or opening the outside air supply duct, - a second step of measuring a second variable representative of the air quality by the sensor, the valve being in a second position of closing or opening of the outside air supply duct, different from the first position, - a third step of calculating the difference between the second variable and the first variable to deduce a gap, and - a fourth step of comparison between the deviation and a threshold value to check if the sensor is working correctly.

[0015] The invention thus provides a method for diagnosing a sensor intended to measure a variable representative of the quality of the air passing through an air supply circuit of a motor vehicle passenger compartment, making it possible to easily and quickly detect a faulty sensor.

[0016] The method consists of verifying that the sensor detects a change in air quality between the open and closed states of the air flow control valve.

[0017] In other words, if the sensor actually detects a change in the air quality between the passage of the air flow control valve from the closed state to the open state or from the open state to the closed state, this means that the sensor is operational.

[0018] Thus, the after-sales service is able to diagnose a failure of one of the sensors in a minimum of time.

[0019] A time saving is therefore achieved in after-sales service, resulting in an economic gain.

[0020] Since a sensor failure is detected quickly, the risk to the health of vehicle occupants is reduced.

[0021] According to a variant, during the first measurement step, the valve is closed, the valve being open during the second measurement step. The sensor measurements are considered consistent if the difference between the second variable and the first measured variable is strictly greater than the threshold value.

[0022] According to a variant, during the first measurement step, the valve is open, the valve being closed during the second measurement step. The sensor measurements are considered consistent if the difference between the second variable and the first measured variable is strictly less than the threshold value.

[0023] According to a variant, the sensor is a particle rate sensor measuring particle sizes contained in the air flow passing through the outside air supply duct or a sensor measuring the level of ozone or nitrogen dioxygen or sulfur dioxide or carbon monoxide in the air flow passing through the outside air supply duct. The first and second variables are a particle rate or an ozone rate or a nitrogen dioxygen rate or a sulfur dioxide rate or a carbon monoxide rate.

[0024] According to one variant, the outside air supply duct comprises a particle rate sensor measuring particle sizes, a sensor measuring the ozone rate, a sensor measuring the nitrogen dioxide rate, a sensor measuring the sulfur dioxide rate and a sensor measuring the carbon monoxide rate. The first, second, third and fourth steps are applied simultaneously for each sensor in order to diagnose all the sensors simultaneously.

[0025] This allows to reduce the diagnostic time.

[0026] According to a variant, the vehicle comprises openings in the closed position during the first and second measurement steps.

[0027] This allows for more accurate measurement of pollutants.

[0028] According to a variant, two successive test series each comprising at least the first and second measurement steps are carried out after a time interval of at least 10 seconds.

[0029] This allows time for the new air flow to circulate in the duct outdoor air supply and ensure a variation in the pollutant rate.

[0030] According to one variant, the threshold value is between 5% and 15% of the difference between the first and second variables.

[0031] This range of values ​​is optimal for detecting a significant detection fault.

[0032] According to a variant, the number of malfunctions is counted for each sensor. A fault code is stored in a memory when the number of malfunctions exceeds a counting threshold. Each sensor has a separate fault code.

[0033] This allows rapid detection of the malfunction of one of the sensors.

[0034] The invention also relates to a vehicle implementing the diagnostic method as defined above. The sensor and the valve are connected to a computer of the vehicle.

[0035] An embodiment of the present invention will be described below, by way of non-limiting examples, with reference to the single appended figure in which:

[0036] [Fig. 1] schematically illustrates an air supply circuit for a motor vehicle passenger compartment.

[0037] In the remainder of the description, elements having an identical structure or similar functions are designated by the same reference.

[0038] [Fig.l] illustrates an air supply circuit 1 for a passenger compartment 3 of a motor vehicle.

[0039] The supply circuit 1 comprises an aerator, for example positioned in the upper part of the passenger compartment 3, in particular at the level of the awning of the motor vehicle.

[0040] The supply circuit 1 comprises an outside air supply duct 4, called an “outside air inlet duct”, which connects the aerator to an air pulsation fan 7, diffusing the air into the passenger compartment 3.

[0041] The outside air supply duct 4 comprises a filtration device 5 comprising at least one filter, for example, chosen from the group containing: a pollen filter, an activated carbon filter, an anti-allergen filter, a particle filter.

[0042] Depending on the level of finish, equipment or options of the motor vehicle, the motor vehicle includes one or more of the filters listed in the aforementioned group.

[0043] More generally, the filter designates equipment designed to filter, in the air which feeds it, at least one chemical species in solid form, for example fine particles or dust, or in gaseous form, comprising for example carbon monoxide (CO), sulfur dioxide (SO2), ozone (03), nitrogen dioxide (NO2), carbon dioxide (CO2), oxygen (02).

[0044] The filter may also include, in addition or as a variant, a function of dehumidifying the air passing through it.

[0045] The filtered air is conveyed through the outside air supply duct 4 to the vent 7 air pulsation fan, designed to draw in filtered air and distribute it into the passenger compartment 3.

[0046] The supply circuit 1 further comprises a passenger compartment duct 8, forming a loop between the passenger compartment 3 of the motor vehicle and the exterior air supply duct 4 for recycling the air from the passenger compartment 3.

[0047] In the exemplary embodiment of the supply circuit 1 illustrated in [Fig.l], the passenger compartment duct 8 comprises a filtration assembly 9 designed to filter the air circulating from the passenger compartment 3 to the outside air supply duct 4.

[0048] For example, the filtration assembly 9 comprises a small filter which has the function of cleaning the air coming from the passenger compartment 3.

[0049] According to an alternative embodiment not shown, the passenger compartment duct 8 does not include any filtration assembly 9.

[0050] The outside air supply duct 4 comprises a valve 6 for controlling the air flow, for example a three-way valve, called a “Y valve”, designed and arranged for: • close the passenger compartment duct 8 so that all the air entering the motor vehicle is admitted via the outside air supply duct 4, or • close the outside air supply duct 4 in order to prevent outside air from entering the passenger compartment 3, for example when the user of the motor vehicle operates the supply circuit in “recycling” mode, for example when the motor vehicle passes through a polluted tunnel, or • admit into the outside air supply duct 4 air coming both from outside the motor vehicle and air coming from the passenger compartment 3 in order to allow a partial renewal of the air and to begin to bring the air coming from outside the motor vehicle to the temperature of the passenger compartment 3.

[0051] In the embodiment illustrated in [Fig.l], the air flow control valve 6 is mounted downstream of the filtration device 5, the upstream and downstream being understood relative to the direction of air flow in the supply circuit 1, i.e. from the outside to the inside of the passenger compartment 3.

[0052] The supply circuit 1 comprises at least one sensor 2 intended to measure a variable representative of the quality of the air passing through the air supply circuit 1 of the passenger compartment 3 of the motor vehicle. The sensor 2 is mounted in the exterior air supply duct 4, downstream of the valve 6, that is to say between the valve 6 and the air pulsation fan 7.

[0053] The sensor 2 may be a particle rate sensor measuring particle sizes particles contained in the air flow passing through the outside air supply duct 4.

[0054] The particle rate sensor is an optical sensor designed to measure the content of particles less than 2.5 pm or less than 10 pm contained in the air passing through it.

[0055] In this regard, the particle rate sensor is also called a “PM2.5” sensor or a “PM 10” sensor.

[0056] The operating principle is as follows: air passes through a housing containing an infrared light emitter and the particle rate sensor measures the content of these particles contained in the air by measuring the quantity of light reflected by the particles. The wavelength of the light source makes it possible to distinguish the particle sizes, this distinction being materialized on the pulse pattern of the output voltage of the optical sensor, which makes it possible to distinguish between the particles.

[0057] The sensor 2 may also be a sensor measuring the level of ozone (03) or nitrogen dioxide (NO2) or sulfur dioxide (SO2) or carbon monoxide (CO) in the air flow passing through the outside air supply duct 4, for example.

[0058] The sensor 2 may be an air quality control sensor, known as “AQS”, an acronym for “Air Quality System”.

[0059] The air quality monitoring sensor is capable of measuring the levels of carbon monoxide (CO), sulfur dioxide (SO2), ozone (03), and nitrogen dioxide (NO2) at the same time.

[0060] Preferably, the outside air supply duct 4 comprises a particle rate sensor measuring particle sizes of 2.5 μm and 10 μm, and an air quality monitoring sensor measuring the levels of carbon monoxide (CO), sulfur dioxide (SO2), ozone (03), and nitrogen dioxide (NO2).

[0061] The invention relates to a method for diagnosing at least one sensor 2 intended to measure a variable representative of the quality of the air passing through the air supply circuit 1 of the passenger compartment 3 of the motor vehicle.

[0062] The diagnostic method is implemented by hardware and software means integrated into the motor vehicle.

[0063] For this purpose, the software means include in particular the algorithm implemented to execute the method of the invention.

[0064] The software means are for example integrated into a motor vehicle computer, for example in the electronic management box known under the name “BSI”, acronym for “Intelligent Servitude Box”.

[0065] The diagnostic method comprises: - a first step of measuring a first variable representative of the air quality by the sensor 2, the valve 6 being in a first position of closing or opening the outside air supply duct 4, - a second step of measuring a second variable representative of the air quality by the sensor 2, the valve 6 being in a second position of closing or opening of the outside air supply duct 4, different from the first position, - a third step of calculating the difference between the second variable and the first variable to deduce a gap, and - a fourth step of comparison between the deviation and a threshold value to deduce whether the measurements from sensor 2 are consistent.

[0066] The first and second variables are a particle rate if the sensor 2 is a particle rate sensor or an ozone rate if the sensor 2 is a sensor measuring the ozone rate or a nitrogen dioxide rate if the sensor 2 is a sensor measuring the nitrogen dioxide rate or a sulfur dioxide rate if the sensor 2 is a sensor measuring the sulfur dioxide rate or a carbon monoxide rate if the sensor 2 is a sensor measuring the carbon monoxide rate.

[0067] As previously stated, preferably, the outside air supply duct 4 comprises a particle rate sensor measuring particle sizes of 2.5 μm and 10 μm, a sensor measuring the ozone rate, a sensor measuring the nitrogen dioxide rate, a sensor measuring the sulfur dioxide rate and a sensor measuring the carbon monoxide rate.

[0068] The diagnostic method is applied for all sensors. In other words, the first, second, third and fourth steps are carried out simultaneously for each sensor 2 in order to diagnose all sensors 2 simultaneously.

[0069] Two successive test series each comprising at least the first and second measurement steps are carried out at a time interval of at least 10 seconds. The time interval is calibratable.

[0070] Alternatively, the sensors 2 can be diagnosed successively. The diagnostic method is then carried out sensor 2 by sensor 2.

[0071] The vehicle includes openings which are closed during the first and second measurement steps. The computer must receive information that the openings are closed, otherwise these steps are not carried out.

[0072] According to a variant, during the first measurement step, the valve 6 is closed, the valve 6 being open during the second measurement step. The measurements of the sensor 2 are considered consistent if the difference between the second variable and the first measured variable is greater than the threshold value.

[0073] An example of operation is given below.

[0074] The vehicle's openings are all closed and valve 6 is closed.

[0075] In the first measurement step, the particle rate sensor measures first particle levels of 2.5 p and 10 p. The air quality control sensor measures first levels of ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide which are transmitted to the computer.

[0076] In this example, six first rates and therefore six first variables representative of air quality are measured.

[0077] The calculator thus receives a first particle rate of 2.5 p (TPA2.5), a first particle rate of 10 p (TPA10), a first ozone rate (TAO3), a first nitrogen dioxide rate (TANO2), a first sulfur dioxide rate (TASO2) and a first carbon monoxide rate (TACO).

[0078] Valve 6 then changes state and moves to the open position.

[0079] In the second measurement step, the particle rate sensor measures second particle rates of 2.5 p and 10 p and the air quality control sensor measures second rates of ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide which are transmitted to the computer.

[0080] In this example, six second rates and therefore six second variables representative of air quality are also measured.

[0081] The calculator thus receives a second particle rate of 2.5 p (TPB2.5), a second particle rate of 10 p (TPB10), a second ozone rate (TBO3), a second nitrogen dioxide rate (TBNO2), a second sulfur dioxide rate (TBSO2) and a second carbon monoxide rate (TBCO).

[0082] The third step of calculating the difference between the second variables and the first variables to deduce a deviation is then applied.

[0083] Six rate differences or gaps are calculated: - DTP2.5 (particle rate deviation of 2.5 p) = TPB2.5 (valve open) -TPA2.5 (valve closed), - DTP10 (particle rate deviation of 10 p) = TPB10 (valve open) -TPA10 (valve closed), - DTO3 (ozone level deviation) = TBO3 (valve open) - TAO3 (valve closed), - DTNO2 (nitrogen dioxygen rate difference) = TBNO2 (valve open) -TANO2 (valve closed), - DTSO2 (sulfur dioxide rate difference) = TBSO2 (valve open) -TASO2 (valve closed), - DTCO (carbon monoxide level difference) = TBCO (valve open) -TACO (valve closed).

[0084] Rate differences are preferably expressed as percentages.

[0085] The fourth step of comparison between the deviation and a threshold value is then applied for each variable representative of the air quality to deduce whether the measurements of the sensors 2 are consistent. Threshold values ​​are defined: - STP2.5 corresponding to the threshold value for the particle rate of 2.5 p, - STP10 corresponding to the threshold value for the particle rate of 10 p, - STO3 corresponding to the threshold value for the ozone rate, - STNO2 corresponding to the threshold value for the nitrogen dioxygen rate, - STSO2 corresponding to the threshold value for the sulfur dioxide rate, - STCO corresponding to the threshold value for the carbon monoxide level.

[0086] Each threshold value is between 5% and 15% of the difference between the first and second variables. Each threshold value is calibrated. All threshold values ​​may have the same percentage difference between the first and second variables or a separate percentage difference for each pollutant.

[0087] After determining the rate differences before and after the change of state of the valve 6, the computer compares the value of the differences with the threshold values ​​for each variable representative of the air quality and thus verifies the reliability of each sensor 2.

[0088] The 2.5 p particle rate sensor is valid if the difference in rate DTP2.5 is strictly greater than the threshold value STP2.5.

[0089] The 10 p particle rate sensor is valid if the difference in rate DTP10 is strictly greater than the threshold value STP10.

[0090] The ozone rate sensor is valid if the difference in DTO3 rate is strictly greater than the STO3 threshold value.

[0091] The nitrogen dioxygen rate sensor is valid if the difference in DTNO2 rate is strictly greater than the STNO2 threshold value.

[0092] The sulfur dioxide rate sensor is valid if the difference in DTSO2 rate is strictly greater than the STSO2 threshold value.

[0093] The carbon monoxide level sensor is valid if the difference in DTCO level is strictly greater than the STCO threshold value.

[0094] Otherwise, for each variable representing air quality, if the difference in rate is strictly lower than the threshold value, sensor 2 is considered to be malfunctioning.

[0095] According to another example, the valve 6 is first opened and then closed. The vehicle's openings are all closed.

[0096] The first, second and third steps are carried out as in the previous example.

[0097] In the first measurement step, the particle rate sensor measures first particle rates of 2.5 p and 10 p and the quality control sensor The air measures the first levels of ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide which are transmitted to the computer, valve 6 being open.

[0098] Valve 6 then changes state and moves to the closed position.

[0099] In the second measurement step, the particle rate sensor measures second particle rates of 2.5 p and 10 p and the air quality control sensor measures second rates of ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide which are transmitted to the computer.

[0100] The third step of calculating the difference between the second variables and the first variables to deduce a deviation is then carried out.

[0101] Six rate differences (or gaps) are obtained: DTP2.5 = TPB2.5 (valve closed) - TPA2.5 (valve open), DTP10 = TPB10 (valve closed) - TPA10 (valve open), DTO3 = TBO3 (valve closed) - TAO3 (valve open), DTNO2 = TBNO2 (valve closed) - TANO2 (valve open), DTSO2 = TBSO2 (valve closed) - TASO2 (valve open), DTCO = TBCO (valve closed) - TACO (valve open).

[0102] The fourth step of comparison between the deviation and a threshold value is then carried out for each variable representative of the air quality to deduce whether the measurements from the sensors 2 are consistent.

[0103] The 2.5p particle rate sensor is valid if the difference in rate DTP2.5 is strictly less than the threshold value STP2.5.

[0104] The 10 p particle rate sensor is valid if the difference in rate DTP10 is strictly less than the threshold value STP10.

[0105] The ozone rate sensor is valid if the difference in DTO3 rate is strictly greater than the STO3 threshold value.

[0106] The nitrogen dioxygen rate sensor is valid if the difference in DTNO2 rate is strictly lower than the STNO2 threshold value.

[0107] The sulfur dioxide rate sensor is valid if the difference in DTSO2 rate is strictly lower than the STSO2 threshold value.

[0108] The carbon monoxide level sensor is valid if the difference in DTCO level is strictly lower than the STCO threshold value.

[0109] Otherwise, for each variable representing air quality, if the difference in rate is strictly greater than the threshold value, sensor 2 is considered to be malfunctioning.

[0110] The first, second, third and fourth steps are repeated several times. The number of malfunctions is counted for each sensor 2. A fault code is stored in a vehicle memory when the number of malfunctions is greater than a counting threshold. Each sensor 2 includes a fault code distinct.

[0111] The counting threshold can be identical for all sensors 2 or different for each sensor 2.

[0112] The counting threshold can be three for all sensors 2, for example.

[0113] The number of malfunctions is counted for the particle rate sensor of 2.5p, for example.

[0114] If the number of malfunctions for the 2.5 p particle rate sensor is greater than 3, a first fault code is stored in the memory.

[0115] If the number of malfunctions for the 10 p particle rate sensor is greater than 3, a second fault code is stored in the memory.

[0116] If the number of malfunctions for the ozone level sensor is greater than 3, a third fault code is stored in the memory.

[0117] If the number of malfunctions for the nitrogen dioxygen rate sensor is greater than 3, a fourth fault code is stored in the memory.

[0118] If the number of malfunctions for the sulfur dioxide level sensor is greater than 3, a fifth fault code is stored in the memory.

[0119] If the number of malfunctions for the carbon monoxide sensor is greater than 3, a sixth fault code is stored in the memory.

[0120] Alternatively, the vehicle service indicator light may be illuminated when a fault code is stored.

[0121] To reset the sensor(s) 2, the associated counters are reset to zero. The sensor(s) 2 can continue to carry out pollutant measurements.

[0122] Preferably, this reset is carried out by an after-sales service.

Claims

Claims

1. Method for diagnosing at least one sensor (2) intended to measure a variable representative of the quality of the air passing through an air supply circuit (1) of a passenger compartment (3) of a motor vehicle, the supply circuit (1) comprising an outside air supply duct (4) connecting the interior to the exterior of the passenger compartment (3), the outside air supply duct (4) comprising a filtration device (5) and a valve (6) for controlling the air flow positioned downstream of the filtration device (5) and intended to close or open the outside air supply duct (4), the sensor (2) being positioned in the outside air supply duct (4), downstream of the valve (6), characterized in that the method comprises: • a first step of measuring a first variable representative of the air quality by the sensor (2),the valve (6) being in a first position of closing or opening the outside air supply duct (4), • a second step of measuring a second variable representative of the air quality by the sensor (2), the valve (6) being in a second position of closing or opening the outside air supply duct (4), different from the first position, • a third step of calculating the difference between the second variable and the first variable to deduce a deviation therefrom, and • a fourth step of comparing the deviation with a threshold value to check whether the sensor (2) is working correctly.,

2. Diagnostic method according to claim 1, characterized in that during the first measurement step, the valve (6) is closed, the valve (6) being open during the second measurement step, the measurements of the sensor (2) being considered consistent if the difference between the second variable and the first measured variable is strictly greater than the threshold value.

3. Diagnostic method according to claim 1, characterized in that during the first measuring step, the valve (6) is open, the valve (6) being closed during the second measuring step, the measurements of the sensor (2) being considered coherent if the difference between the second variable and the first measured variable is strictly less than the threshold value.

4. A diagnostic method according to any one of claims 1 to 3, characterized in that the sensor (2) is a particle rate sensor measuring particle sizes contained in the air flow passing through the outside air supply duct (4) or a sensor measuring the level of ozone or nitrogen dioxide or sulfur dioxide or carbon monoxide in the air flow passing through the outside air supply duct (4), the first and second variables being a particle rate or an ozone rate or a nitrogen dioxide rate or a sulfur dioxide rate or a carbon monoxide rate.

5. A diagnostic method according to any one of claims 1 to 3, characterized in that the outside air supply duct (4) comprises a particle rate sensor measuring particle sizes, a sensor measuring the ozone rate, a sensor measuring the nitrogen dioxide rate, a sensor measuring the sulfur dioxide rate and a sensor measuring the carbon monoxide rate, the first, second, third and fourth steps being applied simultaneously for each sensor (2) in order to diagnose all the sensors (2) simultaneously.

6. Diagnostic method according to any one of claims 1 to 5, characterized in that the vehicle comprises openings in the closed position during the first and second measurement steps.

7. Diagnostic method according to any one of claims 1 to 6, characterized in that two successive test series each comprising at least the first and second measurement steps are carried out after a time interval of at least 10 seconds.

8. Diagnostic method according to any one of claims 1 to 7, characterized in that the threshold value is between 5% and 15% of the difference between the first and second variables.

9. Diagnostic method according to any one of claims 1 to 8, characterized in that the number of malfunctions is counted for each sensor (2), a fault code being stored in a memory when the number of malfunctions is greater than a counting threshold, each sensor (2) comprising a separate fault code.

10. Vehicle, characterized in that it implements the diagnostic method as defined according to any one of claims 1 to 9, the sensor (2) and the valve (6) being connected to a computer of the vehicle.

Images