Method for diagnosing and cleaning sensors for motor vehicles

Abstract

The invention relates to a method for diagnosing a sensor for a motor vehicle and said vehicle (1), said method being notable in that it comprises: a) a detection step (E0) of detecting an error in the measurements implemented by the sensor (30); b) a first phase (P1) of commanding a cleaning of the sensor (30); c) a cancellation step (E4) of cancelling the detection of an error in the measurements of the sensor (30) if the difference between a first variation of the richness level determined on the basis of a parameter relating to the pumped airflow and a second variation determined on the basis of a variation of the voltage of the terminals of the sensor (30) is: i) less than a predefined maximum tolerance threshold; and ii) greater than a predefined minimum tolerance threshold.

Description

Technical Field

[0001] This invention relates to the field of thermal engine vehicles, and more precisely, to a method for diagnosing and cleaning a sensor configured to measure the amount of oxygen leaving a thermal engine of a vehicle. Background Technology

[0002] In a known manner, the vehicle's thermal engine is connected to an exhaust pipe, which specifically allows exhaust gases emitted during the combustion phase of the thermal engine to be released via the exhaust pipe. Furthermore, the exhaust pipe includes a decontamination system, which allows contaminants from the exhaust gases emitted by the thermal engine to be reduced before they are released.

[0003] Furthermore, the sensor is installed between the outlet of the thermal engine and the inlet of the decontamination system, and is particularly capable of measuring the oxygen ratio in the exhaust gas. The oxygen ratio measured by the sensor allows determination of the fuel richness level in the air-fuel mixture injected into the engine.

[0004] In a known manner, the vehicle includes an engine control unit that controls various actuators of the thermal engine, particularly the injectors, air intake flaps, etc.

[0005] The control unit therefore determines the amount of fuel to be injected into the heat engine based on the oxygen ratio measured by sensors, so that the ratio between fuel and air is optimal during the combustion phase of the heat engine, thus ensuring maximum efficiency of the heat engine.

[0006] Before being installed in the vehicle, the sensor is encapsulated in an inert atmosphere. In other words, the sensor is stored in an atmosphere composed of inert gas to prevent oxidation of the sensor's measuring electrodes. However, the inert gas itself adheres to the sensor's electrodes, and this is allegedly "contaminates" the sensor.

[0007] When a sensor is installed in a vehicle, the control unit performs a diagnostic check on the sensor; in other words, the control unit detects whether the measurements taken by the sensor are correlated with each other, and thus whether the sensor is functioning correctly. When the measurements are not correlated, the control unit systematically advises the vehicle owner to replace the oxygen sensor, particularly by displaying an illuminated indicator on the vehicle's dashboard.

[0008] Therefore, as a precaution, vehicle owners will need to replace or replace the sensor, which will incur costs, especially the cost of a new sensor or even the installation of a new sensor.

[0009] The detection of irrelevance in measurements achieved by the sensor can be attributed to either a fault in the sensor itself or inert gas deposited on the sensor's electrodes. However, in the latter case, the contamination of the sensor electrodes by inert gas is reversible, and the sensor will therefore needlessly be replaced, resulting in unnecessary costs and disposal.

[0010] Therefore, there is a need for solutions that allow for at least partial resolution of these shortcomings. Summary of the Invention

[0011] This invention relates to a method for diagnosing sensors used in a motor vehicle, the vehicle comprising:

[0012] -Heat engine;

[0013] - A decontamination system, which is fluidly connected to the engine and configured to decontaminate the exhaust gas originating from the engine;

[0014] - A sensor, which is placed between the engine outlet and the decontamination system inlet, and is configured to measure a parameter related to the oxygen ratio in the exhaust gas leaving the engine, the sensor including two voltage measurement terminals;

[0015] - A computer, which includes a memory area in which the value of a counter is stored;

[0016] The method is noteworthy in that it includes:

[0017] a. Detection steps: Detect the measurement error achieved by the sensor;

[0018] b. First stage: Command to clean the sensor;

[0019] c. Increment step: Increment the counter value with each command used to clean the sensor;

[0020] d. Second stage: This stage, following sensor cleaning, includes:

[0021] i. The operation of the heat engine is controlled by continuously increasing the richness level setpoint sent to the heat engine from a minimum to a maximum value, the richness level being defined by the ratio between the mass of fuel introduced into the heat engine and the theoretical fuel mass requirement for the total combustion of said fuel for a predetermined mass of air injected into the heat engine;

[0022] ii. In sync with the control:

[0023] 1. Measure changes in parameters related to the oxygen ratio;

[0024] 2. Measure the voltage change between the terminals of the sensor;

[0025] iii. Determining the steps: Based on the determined changes in the oxygen ratio-related parameters, determine the first change in the abundance level;

[0026] iv. Determine the steps: Determine the second change in richness level based on the measurement of the voltage change between the voltage measurement terminals of the sensor;

[0027] e. Cancellation Step: If the difference between the determined first change and the determined second change in richness level is as follows, then the detection of the sensor's measurement error is cancelled:

[0028] i. Less than the pre-defined maximum tolerance threshold; and

[0029] ii. Greater than the pre-defined minimum tolerance threshold;

[0030] f. Otherwise, confirm the following steps: If the counter value is greater than the maximum threshold of the predefined cleaning cycle, then confirm that a sensor malfunction has been detected.

[0031] Therefore, the method allows for the distinction between a sensor contaminated by inert gases present in the sensor storage area before installation in the vehicle and a sensor malfunction not attributable to contamination. This allows the vehicle user to be informed of a sensor malfunction only when it occurs, rather than when the sensor is temporarily contaminated. The vehicle user will only replace the sensor if necessary. Furthermore, in the case of sensor contamination, the method allows for sensor cleaning.

[0032] In an advantageous manner, the first phase of the command to clean the sensor specifies that the operation of the thermal engine is controlled by periodically changing the richness level setpoint from a minimum to a maximum value.

[0033] Preferably, the second stage includes a storage sub-step: storing a first change and a second change in the richness level in a memory area. In this way, the first change and the second change are saved and can be compared by a computer to implement a cancellation step or a confirmation step.

[0034] Preferably, the first stage is implemented if the temperature in the decontamination system is higher than a predetermined temperature threshold. This means that the optimal operating temperature has been reached in the decontamination system.

[0035] The present invention also relates to a computer program product, characterized in that it includes a set of program code instructions, which, when executed by one or more processors, configure the one or more processors to implement the previously described method.

[0036] The present invention also relates to a computer for a vehicle, the vehicle comprising:

[0037] -Heat engine;

[0038] - A decontamination system, which is fluidly connected to the engine and configured to decontaminate the exhaust gas originating from the engine;

[0039] - A sensor is placed between the engine outlet and the decontamination system inlet and is configured to measure a parameter related to the oxygen ratio in the exhaust gas leaving the engine.

[0040] The computer is configured to communicate with sensors, and includes a memory region storing predetermined values ​​of counters and a correspondence table, the correspondence table including a set of parameter values, each parameter value being associated with a richness level value, and the computer is configured to implement the previously proposed method.

[0041] The present invention also relates to a motor vehicle, comprising:

[0042] -Heat engine;

[0043] - A decontamination system, which is fluidly connected to the engine and configured to decontaminate the exhaust gas originating from the engine;

[0044] - A sensor is placed between the engine outlet and the decontamination system inlet and is configured to measure a parameter related to the oxygen ratio in the exhaust gas leaving the engine.

[0045] -The computer mentioned earlier. Attached Figure Description

[0046] Further features and advantages of the invention will become more apparent upon reading the following description. This description is purely illustrative and should be read with reference to the accompanying drawings, in which:

[0047] [ Figure 1 ] Figure 1 This is a diagram of a vehicle according to the present invention;

[0048] [ Figure 2 ] Figure 2 The illustration shows the method according to the present invention. Detailed Implementation

[0049] vehicle

[0050] Reference Figure 1 An embodiment of the vehicle 1 according to the present invention will now be presented.

[0051] In a known manner, vehicle 1 includes a thermal engine 10, a decontamination system 20, sensors 30, and a computer 40.

[0052] engine

[0053] In a known manner, the thermal engine 10 allows for the movement of the vehicle 1. For this purpose, the thermal engine 10 generates mechanical energy from a mixture of fuel and air (and more precisely, from the combustion of that mixture). This combustion also produces exhaust gases, particularly including carbon dioxide, water, oxygen, nitrogen, carbon monoxide, hydrocarbons, and nitrogen oxides.

[0054] Decontamination system

[0055] The decontamination system 20 is fluidly connected to the heat engine 10. More precisely, the decontamination system 20 is connected to the heat engine 10 via pipes (especially tubular structures) that allow exhaust gases emitted by the heat engine 10 to move within the decontamination system 20.

[0056] The decontamination system 20 is configured to decontaminate the exhaust gas emitted by the thermal engine 10, in other words, to convert polluting gases (especially carbon monoxide, hydrocarbons or nitrogen oxides included in the exhaust gas) into gases that are harmless to the environment.

[0057] For this purpose, the decontamination system 20 may include, in particular, a particulate filter. As the name suggests, a particulate filter allows the filtration of particles emitted in the exhaust gas so that these particles are not subsequently emitted into the environment of the vehicle 1.

[0058] The decontamination system 20 may also include other systems, such as a module called "RCS" (for "reduction catalytique sélective") and an oxidation catalytic converter.

[0059] The RSC module, as known to those skilled in the art, particularly allows for the reduction of the amount of nitrogen oxides contained in the exhaust gas. As for the oxidation catalytic converter, it allows for the conversion of carbon monoxide and hydrocarbons present in the exhaust gas into substances harmless to the environment of vehicle 1 via oxidation.

[0060] The cleaning system 20 also includes a temperature measuring device 21, which is capable of measuring the internal temperature of the cleaning system 20 and transmitting each measured value to the computer 40.

[0061] sensor

[0062] Sensor 30 is placed between the outlet of the heat engine 10 and the inlet of the decontamination system 20. More precisely, sensor 30 is placed on the tubular pipe connecting the heat engine 10 and the decontamination system 20.

[0063] More precisely, sensor 30 is placed between the outlet of thermal engine 10 and the inlet of particulate filter of decontamination system 20.

[0064] Sensor 30 may be, for example, a sensor known to those skilled in the art as an "oxygen sensor" or "lamb sensor" or even an "upstream sensor".

[0065] More precisely, sensor 30 includes a pumping unit. Sensor 30 is fluidly connected via the pumping unit to a conduit connecting the thermal engine 10 and the decontamination system 20. In other words, exhaust gas moving between the thermal engine 10 and the decontamination system 20 also circulates within the pumping unit of sensor 30.

[0066] Sensor 30 is configured to measure a parameter relating to the oxygen ratio in the exhaust gas leaving the heat engine 10, and especially in the exhaust gas circulating from the heat engine 10 to the decontamination system 20 via pipes. The oxygen ratio in the exhaust gas also allows for the determination of the oxygen concentration in the exhaust gas.

[0067] The parameter specifically corresponds to the so-called "pumping" airflow. The pumping airflow specifies the airflow supplied to the pumping unit as the exhaust gas circulates within it. More precisely, the pumping airflow is attributed to the movement of oxygen (and more precisely, oxygen ions) in the exhaust gas within the pumping unit.

[0068] The pumped airflow specifically represents the difference between the oxygen ratio in the exhaust gas and a reference oxygen ratio. The reference oxygen ratio defines the oxygen ratio emitted by the thermal engine 10 in the exhaust gas following the combustion of the air-fuel mixture, wherein the air quantity is the necessary and sufficient amount relative to the amount of fuel used to allow for complete combustion of the fuel.

[0069] Sensor 30 is also configured to transmit at least one measured value of a first parameter related to the oxygen ratio to computer 40 over a communication link. The communication link is, in particular, a CAN (Controller Area Network) data bus.

[0070] Voltage measuring device 31

[0071] In addition, sensor 30 includes two voltage measurement terminals or electrodes. More precisely, the pumping unit of sensor 30 includes a so-called "reference" unit, which includes two voltage measurement terminals.

[0072] The sensor 30 also includes a voltage measuring device 31, which is capable of measuring the voltage between the voltage measuring terminals of the sensor 30.

[0073] Computer 40

[0074] Computer 40 is configured to communicate with sensor 30 via a communication link. Computer 40 is also configured to communicate with temperature measuring device 21 and voltage measuring device 31.

[0075] In addition, the computer 40 is configured to send instructions to the heat engine 10.

[0076] The computer 40 includes a memory area in which a predetermined value for a counter is stored.

[0077] Furthermore, a predefined correspondence table is stored in the memory area of ​​computer 40. For each value of the parameter (in other words, the pumping airflow), the correspondence table includes the associated richness level value.

[0078] The abundance level is defined for the pre-limited air intake in the thermal engine by the ratio of the actual fuel mass to the theoretical fuel mass injected into the thermal engine 10.

[0079] Theoretical fuel mass limits the necessary and sufficient amount of fuel to ensure total combustion of fuel in a predetermined amount of air intake.

[0080] The abundance level can also be defined by the ratio of the actual fuel mass injected into the thermal engine 10 to the actual air mass introduced into the thermal engine 10.

[0081] For example, when the pumped airflow is positive, or its value is relatively high, the richness level is less than 1. This means that before combustion, the fuel and air mixture injected into the heat engine 10 contains less actual fuel mass than the theoretical fuel mass. Thus, the air and fuel mixture previously injected into the heat engine 10 is fuel-poor.

[0082] Conversely, when the pumped airflow is negative, or its value is relatively low, the abundance level is greater than 1. This means that before combustion, the fuel and air mixture injected into the heat engine 10 includes an actual fuel mass greater than the theoretical fuel mass. Thus, the air and fuel mixture previously injected into the heat engine 10 is considered fuel-rich.

[0083] Computer 40 is configured to receive the value of the pumped airflow supplied to the pumping unit and is configured to determine the richness level value based on the received value of the pumped airflow.

[0084] The computer 40 is also configured to obtain the value of the voltage measured by the measuring device 31 between the voltage measuring terminals, and to determine the value of the richness level based on the received voltage value.

[0085] When the difference between the richness levels determined above is greater than a predefined maximum threshold or less than a predefined minimum threshold, the computer 40 is able to detect measurement errors and more accurately measure relevance and / or reasonableness.

[0086] The computer 40 is also configured to receive the temperature value in the cleaning system 20, which is measured by the temperature measuring device 21. Furthermore, the computer 40 is able to determine whether the received value exceeds a predetermined temperature threshold, specifically limited to 350°C, and thus determine whether the cleaning system 20 is operating within an effective temperature range.

[0087] The computer 40 is also configured to control the operation of the heat engine 10.

[0088] For example, computer 40 is configured to continuously increase the richness level setpoint from the minimum to the maximum value.

[0089] The "continuous" option specifies a set of richness levels between the minimum and maximum values, defined by a step size of 0.005.

[0090] The minimum value is exactly equal to 0.75, and the maximum value is exactly equal to 1.25.

[0091] As a further example, when computer 40 commands sensor 30 to be cleaned, computer 40 controls the operation of thermal engine 10 by periodically changing the richness level setpoint from a minimum to a maximum value. More precisely, the richness level setpoint corresponds to a toothed signal that alternates between a high state where its value is equal to the maximum and a low state where its value is equal to the minimum.

[0092] Computer 40 is configured to receive, in particular continuously, values ​​measured by sensor 30 via a communication link. Computer 40 is also configured to determine a first change in richness level based on the received values ​​measured by sensor 30, to which computer 40 applies a predefined correction factor, and based on a correspondence table.

[0093] The correction factor is predefined by the computer 40 itself in order to correct potential errors in the measurements performed by the sensor 30 according to the environment.

[0094] Computer 40 is also configured to receive values ​​successively measured by voltage measuring device 31. In other words, computer 40 receives changes in voltage measured by voltage measuring device 31. Computer 40 is also configured to determine a second change in richness level based on the measurement of the received voltage changes.

[0095] The computer 40 is configured to increment the value of a counter with each command given for cleaning the sensor 30.

[0096] In this case, the computer 40 is configured to: cancel the detection of the presence of error in the sensor 30 if the difference between a first change in the abundance level determined based on parameters related to the pumped airflow and a second change determined based on the change in voltage between the voltage measurement terminals of the sensor 30 is as follows:

[0097] a. Less than the pre-defined maximum tolerance threshold; and

[0098] b. Greater than the pre-defined minimum tolerance threshold.

[0099] Conversely, if the counter value exceeds a predefined maximum threshold for a cleaning cycle, the computer 40 can confirm a malfunction in the sensor 30. Furthermore, the computer 40 can send a warning signal to the user of the vehicle 1, for example, by sending a light or sound signal to the vehicle's dashboard, to indicate a malfunction in the sensor 30.

[0100] Computer 40 is particularly analogous to diagnostic equipment and is often referred to as “OBD”, which stands for “On-Board Diagnostics” in English.

[0101] Computer 40 includes a processor that is capable of implementing a set of instructions that allows these functions to be performed.

[0102] method

[0103] Reference Figure 2 A method for diagnosing the sensor 30 for the motor vehicle 1, implemented by the computer 40 as described above, will now be proposed.

[0104] The method is implemented after the new sensor 30 is installed in vehicle 1. This may specifically involve installing sensor 30 in vehicle 1 before it leaves the factory or replacing sensor 30 after a fault is detected in a previous sensor installed in vehicle 1. Preferably, the method is implemented when the vehicle is stationary (e.g., in a garage).

[0105] The method first includes a detection step E0: detecting the operational error of sensor 30. For this purpose, computer 40 receives the value of the pumped airflow supplied to the pumping unit and determines an abundance level value based on the received pumped airflow value. Computer 40 also receives the voltage between the voltage measurement terminals of sensor 30 (and more precisely, the reference unit of sensor 30), and also determines an abundance level value based on the received voltage. When the difference between the above-determined abundance level values ​​is greater than a predetermined maximum threshold or less than a predetermined minimum threshold, computer 40 detects a measurement error.

[0106] The method further includes a receiving step E1: the computer 40 periodically receives temperature values ​​from the decontamination system 20, the values ​​being measured by the temperature measuring device 21. The computer 40 then compares each received temperature value with a predetermined temperature threshold.

[0107] When the temperature in the decontamination system 20 is higher than a predetermined temperature threshold, the method includes a first stage P1: commanding the sensor 30 to be cleaned, during which the computer 40 controls the operation of the thermal engine 10 by causing the abundance level setpoint sent to the thermal engine 10 to periodically change from a minimum value to a maximum value, and vice versa.

[0108] For example, the richness level setpoint changes from its minimum to its maximum value every second, and vice versa. In other words, the richness level setpoint is constrained to its minimum value over a period of one second, and then to its maximum value over a period of one second, and vice versa.

[0109] Following the first stage P1, the method includes a second stage P2: controlling the operation of the thermal engine 10.

[0110] Therefore, the second stage P2 includes a control sub-step E21: controlling the operation of the thermal engine 10 by continuously increasing the richness level setpoint from the minimum to the maximum value. In other words, the computer 40 sends a series of richness level setpoints to the thermal engine 10, and the richness level value for these setpoints is increased regularly.

[0111] For each received richness level setpoint, the thermal engine 10 adapts its operation to conform to the richness level setpoint.

[0112] The second stage P2 also includes a measurement sub-step E22: synchronously with the control sub-step E21, parameters are periodically measured by the sensor 30. Furthermore, each value measured by the sensor 30 is transmitted to the computer 40.

[0113] The second stage P2 also includes a measurement sub-step E23: the voltage between the voltage measurement terminals of the sensor 30 is measured synchronously by the voltage measuring device 31 and the control sub-step E21. Each value measured by the voltage measuring device 31 is transmitted to the computer 40.

[0114] Therefore, the second stage P2 also includes a receiving sub-step E24: the computer 40 receives each parameter value transmitted by the sensor 30 and each voltage value measured between the voltage measurement terminals of the sensor 30.

[0115] For each received parameter value, the second stage P2 includes a determination sub-step E25: the computer 40 determines the richness level based on the parameter value and a correspondence table stored in a memory area. Thus, during the operation of the thermal engine 10, and especially when a sequence of richness level setpoints is sent to the thermal engine 10, the computer 40 has determined the first change in the richness level.

[0116] For each received measured voltage value, the second stage P2 further includes a determination sub-step E26: determining the abundance level based on the received measured voltage value. Therefore, the computer 40 determines a second change in the abundance level based on the measurement of the voltage change between the voltage measurement terminals of the sensor 30 by the voltage measuring device 31.

[0117] The second stage P2 then includes the storage stage E27: storing the first and second changes of richness level in the memory area.

[0118] The method includes an incrementing step E3: each time the first stage P1 of the command to clean sensor 30 is executed, the value of the counter is incremented.

[0119] The method also includes canceling step E4: if the difference between a first change in abundance level determined based on parameters related to the pumped airflow and a second change determined based on a change in voltage between the voltage measurement terminals of sensor 30 is such that the detection of measurement error by sensor 30 is canceled:

[0120] a. Less than the pre-defined maximum tolerance threshold; and

[0121] b. Greater than the pre-defined minimum tolerance threshold.

[0122] In other words, canceling the detection of measurement error by sensor 30 means that sensor 30 has been cleaned and there is no problem with its operation; it is simply contaminated.

[0123] Conversely, when the detection of error in the measurement by sensor 30 is not cancelled, the method includes a confirmation step E5: if the value of the counter is greater than (particularly limited to between 2 and 10, preferably 5) a maximum threshold of a predefined cleaning cycle, then a fault in sensor 30 is confirmed. Therefore, in this case, it means that although cleaning of sensor 30 was previously performed, the operation of sensor 30 has not changed. Therefore, it does not involve a contamination problem of sensor 30 but rather a fault within sensor 30.

[0124] After confirming step E5, the method may include sending step E6: in particular, sending an alarm signal to the user of vehicle 1 via an audible or visual signal on the dashboard to notify the user to replace sensor 30 or to have it replaced.

Claims

1. A method for diagnosing a sensor (30) for a motor vehicle (1), the vehicle (1) comprising: -Thermal Engine (10); - A decontamination system (20) is fluidly connected to the engine (10) and configured to decontaminate exhaust gases originating from the engine (10); - A sensor (30) is placed between the outlet of the engine (10) and the inlet of the decontamination system (20) and is configured to measure a parameter related to the oxygen ratio in the exhaust gas leaving the engine (10). The sensor (30) includes two voltage measurement terminals. - Computer (40), which includes a memory area in which the value of a counter is stored; The method is characterized in that it includes: a) Detection step (E0): Detect the error of the measurement performed by the sensor (30); b) First stage (P1): Command to clean sensor (30); c) Incremental step (E3): During each command used to clean the sensor (30), The value of the incrementing counter; d) Second stage (P2): This stage, following the cleaning of the sensor (30), includes: i) The operation of the heat engine (10) is controlled by continuously increasing the richness level setpoint sent to the heat engine (10) from a minimum to a maximum value, the richness level being defined by the ratio between the mass of fuel introduced into the heat engine (10) and the theoretical fuel mass requirement for the total combustion of said fuel for a predetermined mass of air injected into the heat engine (10). ii) Synchronously with control (E21): 1) The change in parameters related to the oxygen ratio is measured by sensor (30) (E22); 2) Measure the change in voltage between the voltage measurement terminals of the (E23) sensor (30); iii) Determine the first change in abundance level based on the determined change in the oxygen ratio-related parameter; iv) Determine step (E26): Determine a second change in the richness level based on the measurement of the change in voltage between the voltage measurement terminals of the sensor (30); e) Cancel step (E4): If the difference between the determined first change and the determined second change in richness level is the following, then the detection of the measurement error of the sensor (30) is canceled: i) Less than the pre-defined maximum tolerance threshold; and ii) Greater than the pre-defined minimum tolerance threshold; f) Otherwise, confirm step (E5): If the value of the counter is greater than the maximum threshold of the predefined cleaning cycle, then confirm that a fault has been detected in the sensor (30).

2. The method as claimed in the preceding claim, wherein, The first stage (P1) of the command to clean the sensor (30) specifies that the operation of the thermal engine (10) is controlled by periodically changing the richness level setpoint from the minimum to the maximum value.

3. The method as described in any of the preceding claims, wherein, The second stage (P2) includes a storage sub-step (E27): storing the first and second changes in richness levels in the memory region.

4. The method as described in any of the preceding claims, wherein, If the temperature in the decontamination system is higher than the predetermined temperature threshold, then the first stage (P1) is implemented.

5. A computer program product, characterized in that: It includes a set of program code instructions that, when executed by one or more processors, configure the one or more processors to implement the method as described in any of the preceding claims.

6. A computer (40) for a vehicle (1), the vehicle (1) comprising: -Thermal Engine (10); - A decontamination system (20) is fluidly connected to the engine (10) and configured to decontaminate exhaust gas originating from the engine (10); - A sensor (30) is placed between the outlet of the engine (10) and the inlet of the decontamination system (20) and is configured to measure a parameter related to the oxygen ratio in the exhaust gas leaving the engine (10). The computer (40) is configured to communicate with the sensor (30), the computer (40) includes a memory region therein storing predetermined values ​​of counters and a correspondence table, the correspondence table including a set of parameter values, each parameter value being associated with a richness level value, and the computer (40) is configured to implement the method as described in any one of claims 1 to 4.

7. A motor vehicle (1) comprising: -Thermal Engine (10); - A decontamination system (20) is fluidly connected to the engine (10) and configured to decontaminate exhaust gas originating from the engine (10); - A sensor (30) is placed between the outlet of the engine (10) and the inlet of the decontamination system (20) and is configured to measure a parameter related to the oxygen ratio in the exhaust gas leaving the engine (10). - The computer (40) as described in the preceding claim.

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