Diagnosis method and control unit for performing a diagnosis of a lambda sensor of the UEGO type of an exhaust system for an internal combustion engine

1. A diagnosis method for performing a diagnosis of a lambda sensor of a Universal Exhaust Gas Oxygen (UEGO) type of an exhaust system for an internal-combustion engine, wherein the lambda sensor includes a series of pins (VS+, VS/IP−, IP+, RCOMP) and the diagnosis method comprises steps of:

heating the lambda sensor to cause the lambda sensor to reach an inner temperature that is higher than about 600° C.;

polarizing a first one of the pins (VS/IP−) by connecting the first pin (VS/IP−) to a supply voltage (Vcc) through a first limiting resistance (RLS);

measuring a voltage of all of the pins (VS+, VS/IP−, IP+, RCOMP) while the first pin (VS/IP−) is connected to the supply voltage (Vcc); and

diagnosing a presence of a short circuit to an electrical ground (GND) if the voltage of at least one of the pins (VS+, VS/IP−, IP+, RCOMP) is lower than a predetermined threshold;

wherein the diagnosis method comprises further, after the diagnosis of the presence of the short circuit to the electrical ground (GND) is ended, steps of:

polarizing the first pin (VS/IP−) only by connecting the first pin (VS/IP−) to the supply voltage (Vcc) through the first limiting resistance (RLS);

measuring the voltage of all of the pins (VS+, VS/IP−, IP+, RCOMP) while the first pin (VS/IP−) is connected to the supply voltage (Vcc); polarizing the first pin (VS/IP−) only by connecting the first pin (VS/IP−) to the electrical ground (GND) through a second limiting resistance (RLS); measuring the voltage of all of the pins (VS+, VS/IP−, IP+, RCOMP) while the first pin (VS/IP−) is connected to the electrical ground (GND);

calculating, for each of pine (VS+, VS/IP−, IP+, RCOMP), a voltage difference (ΔV), which is equal to a difference between the voltage measured when the first pin (VS/IP−) was connected to the supply voltage (Vcc) and the voltage measured when the first pin (VS/IP−) was connected to the electrical ground (GND); and

diagnosing the presence of an open circuit if the voltage difference (ΔV) of at least one of the pins (VS+, VS/IP−, IP+, RCOMP) is lower than a predetermined threshold.

2. The diagnosis method according to claim 1 , wherein the first pin (VS/IP−) is polarized by being connected to the supply voltage (Vcc) for a first time interval (T 1 ) ranging from about 8 to about 16 msec.

3. The diagnosis method according to claim 1 , wherein the diagnosis method comprises further, after the heating of the lambda sensor and before the polarization of the first pin (VS/IP), steps of:

polarizing none of the pins (VS+, VS/IP−, IP+, RCOMP) by keeping all of the pins (VS+, VS/IP−, IP+, RCOMP) insulated from the electrical ground (GND) and supply voltage (Vcc);

measuring the voltage of the pins (VS+, VS/IP−, IP+, RCOMP) while none of the pins (VS+, VS/IP−, IP+, RCOMP) is polarized; and

diagnosing the presence of a short circuit to the supply voltage (Vcc) if the voltage of at least one of the pins (VS+, VS/IP−, IP, RCOMP) is higher than a predetermined threshold.

4. The diagnosis method according to claim 3 , wherein the first pin (VS/IP−) is polarized by connecting the first pin (VS/IP−) to the supply voltage (Vcc) only if the presence of a short circuit to the supply voltage (Vcc) has not been previously diagnosed.

5. The diagnosis method according to claim 1 , wherein the diagnosis method comprises further steps of:

diagnosing the presence of an open circuit in the first pin (VS/IP−) if the voltage difference (6V) of all of the other pins (VS+, IP+, RCOMP) is lower than the predetermined threshold; and

diagnosing the presence of an open circuit in other of the pins (VS+, IP+, RCOMP) if the voltage difference (6V) of the first pin (VS/IP−) is higher than the predetermined threshold and the voltage difference (6V) of one of the other pins (VS+, IP+, RCOMP) is lower than the predetermined threshold.

6. The diagnosis method according to claim 1 , wherein the first pin (VS/IP−) is polarized by being connected to the supply voltage (Vcc) and, subsequently, electrical ground (GND) for a second time interval (T 2 ) ranging from about 0.5 to about 2 sec.

7. The diagnosis method according to claim 1 , wherein the first pin (VS/IP−) is polarized by connecting the first pin (VS/IP−) to the supply voltage (Vcc) and electrical ground (GND) only if the presence of a short circuit to the electrical ground (GND) has not been previously diagnosed.

8. The diagnosis method according to claim 1 , wherein the step of heating the lambda sensor involves controlling a heater of the lambda sensor in a substantially open-loop manner with an electric power that is determined by a thermal model of the lambda sensor.

9. The diagnosis method according to claim 1 , wherein the diagnosis method comprises further, only if the presence of a short circuit to the electrical ground (GND) has been previously diagnosed, steps of:

letting the lambda sensor cool down as to cause the lambda sensor to reach an inner temperature that is lower than about 250° C.;

polarizing all of the pins (VS+, VS/IP−, IP+, RCOMP) by connecting all of the pins (VS+, VS/IP−, IP+, RCOMP) to the supply voltage (Vcc) through corresponding third limiting resistances (RHS);

measuring the voltage of all of the pins (VS+, VS/IP−, IP+, RCOMP) while all of the pins (VS+, VS/IP−, IP+, RCOMP) are connected to the supply voltage (Vcc); and

diagnosing the presence of a short circuit to the electrical ground (GND) in the pin (VS+, VS/IP−, IP+, RCOMP) in which the voltage is lower than a predetermined threshold.

10. The diagnosis method according to claim 1 , wherein the diagnosis method comprises further, only if the presence of a short circuit to the supply voltage (Vcc) has been previously diagnosed, steps of:

letting the lambda sensor cool down, to cause the lambda sensor to reach an inner temperature that is lower than about 250° C.;

polarizing all of the pins (VS+, VS/IP−, IP+, RCOMP) by connecting all of the pins (VS+, VS/IP−, IP+, RCOMP) to the electrical ground (GND) through corresponding fourth limiting resistances (RLS);

measuring the voltage of all of the pins (VS+, VS/IP−, IP+, RCOMP) while all of the pins (VS+, VS/IP−, IP+, RCOMP) are connected to the electrical ground (GND); and

diagnosing the presence of a short circuit to the supply voltage (Vcc) in the pin (VS+, VS/IP−, IP+, RCOMP) in which the voltage is higher than a predetermined threshold.

11. The diagnosis method according to claim 9 , wherein the pins (VS+, VS/IP−, IP+, RCOMP) are polarized by being connected to either of the supply voltage (Vcc) and electrical ground (GND) for a third time interval (T 3 ) ranging from about 8 to about 30 msec.

12. The diagnosis method according to claim 9 , wherein the diagnosis method comprises further, after the cooling down of the lambda sensor and before the polarization of all of the pins (VS+, VS/IP−, IP+, RCOMP), steps of:

polarizing none of the pins (VS+, VS/IP−, IP+, RCOMP) by keeping all of the pins (VS+, VS/IP−, IP+, RCOMP) insulated from the electrical ground (GND) and supply voltage (Vcc); measuring the voltage of the pins (VS+, VS/IP−, IP+, RCOMP) while none of the pins (VS+, VS/IP−, IP+, RCOMP) is polarized;

diagnosing the presence of a short circuit to the supply voltage (Vcc) if the voltage of at least one of the pins (VS+, VS/IP−, IP+, RCOMP) is higher than a predetermined threshold; and

diagnosing the presence of a short circuit to the electrical ground (GND) if the voltage of all of the pins (VS+, VS/IP−, IP+, RCOMP) is lower than the predetermined threshold.

13. A control unit ( 6 ) for performing a diagnosis of a lambda sensor of Universal Exhaust Gas Oxygen (UEGO) type of an exhaust system for an internal-combustion engine, wherein the lambda sensor includes a series of pins (VS+, VS/IP−, IP+, RCOMP) and the control unit ( 6 ) comprises:

a first switch (SWHHS) that connects a first pin (VS/IP) to a supply voltage (Vcc) through a first limiting resistance (RHS);

a second switch (SWHLS) that connects the first pin (VS/IP) to an electrical ground (GND) through a second limiting resistance (RHS);

a series of third switches (SWCHS) each of which connects each of the pins (VS+, VS/IP−, IP+, RCOMP) to the supply voltage (Vcc) through a third limiting resistance (RHS);

a series of fourth switches (SWCHS) each of which connects each of the pins (VS+, VS/IP−, IP+, RCOMP) to the electrical ground (GND) through a fourth limiting resistance (RHS); and

a series of reading devices ( 8 ) each of which is permanently connected to a corresponding one of the pins (VS+, VS/IP−, IP++RCOMP) and reads the voltage present in the pin (VS+, VS/IP−, IP+RCOMP).

14. A diagnosis method for performing a diagnosis of a lambda sensor of a Universal Exhaust Gas Oxygen type of an exhaust system for an internal-combustion engine, wherein the lambda sensor includes a series of pins (VS+, VS/IP−, IP+, RCOMP) and the diagnosis method comprises steps of:

heating the lambda sensor to cause the lambda sensor to reach an inner temperature that is higher than about 600° C.;

polarizing a first one of the pins (VS/IP−) by connecting the first pin (VS/IP−) to a supply voltage (Vcc) through a first limiting resistance (RLS);

measuring a voltage of all of the pins (VS+, VS/IP−, IP+, RCOMP) while the first pin (VS/IP−) is connected to the supply voltage (Vcc); and

diagnosing a presence of a short circuit to an electrical ground (GND) if the voltage of at least one of the pins (VS+, VS/IP−, IP+, RCOMP) is lower than a predetermined threshold;

wherein the diagnosis method comprises further, only if the presence of a short circuit to the electrical ground (GND) has been previously diagnosed, steps of:

letting the lambda sensor cool down as to cause the lambda sensor to reach an inner temperature that is lower than about 250° C.;

polarizing all of the pins (VS+, VS/IP−, IP+, RCOMP) by connecting all of the pins (VS+, VS/IP−, IP+, RCOMP) to the supply voltage (Vcc) through corresponding third limiting resistances (RHS);

measuring the voltage of all of the pins (VS+, VS/IP−, IP+, RCOMP) while all of the pins (VS+, VS/IP−, IP+, RCOMP) are connected to the supply voltage (Vcc); and

diagnosing the presence of a short circuit to the electrical ground (GND) in the pin (VS+, VS/IP−, IP+, RCOMP) in which the voltage is lower than a predetermined threshold.

15. The diagnosis method according to claim 14 , wherein the pins (VS+, VS/IP−, IP+, RCOMP) are polarized by being connected to either of the supply voltage (Vcc) and electrical ground (GND) for a third time interval (T 3 ) ranging from about 8 to about 30 msec.

16. The diagnosis method according to claim 14 , wherein the diagnosis method comprises further, after the cooling down of the lambda sensor and before the polarization of all of the pins (VS+, VS/IP−, IP+, RCOMP), steps of:

polarizing none of the pins (VS+, VS/IP−, IP+, RCOMP) by keeping all of the pins (VS+, VS/IP−, IP+, RCOMP) insulated from the electrical ground (GND) and supply voltage (Vcc); measuring the voltage of the pins (VS+, VS/IP−, IP+, RCOMP) while none of the pins (VS+, VS/IP−, IP+, RCOMP) is polarized;

diagnosing the presence of a short circuit to the supply voltage (Vcc) if the voltage of at least one of the pins (VS+, VS/IP−, IP+, RCOMP) is higher than a predetermined threshold; and

diagnosing the presence of a short circuit to the electrical ground (GND) if the voltage of all of the pins (VS+, VS/IP−, IP+, RCOMP) is lower than the predetermined threshold.

17. A diagnosis method for performing a diagnosis of a lambda sensor of a Universal Exhaust Gas Oxygen type of an exhaust system for an internal-combustion engine, wherein the lambda sensor includes a series of pins (VS+, VS/IP−, IP+, RCOMP) and the diagnosis method comprises steps of:

heating the lambda sensor to cause the lambda sensor to reach an inner temperature that is higher than about 600° C.;

polarizing a first one of the pins (VS/IP−) by connecting the first pin (VS/IP−) to a supply voltage (Vcc) through a first limiting resistance (RLS);

measuring a voltage of all of the pins (VS+, VS/IP−, IP+, RCOMP) while the first pin (VS/IP−) is connected to the supply voltage (Vcc); and

diagnosing a presence of a short circuit to an electrical ground (GND) if the voltage of at least one of the pins (VS+, VS/IP−, IP+, RCOMP) is lower than a predetermined threshold;

wherein the diagnosis method comprises further, only if the presence of a short circuit to the supply voltage (Vcc) has been previously diagnosed, steps of:

letting the lambda sensor cool down, to cause the lambda sensor to reach an inner temperature that is lower than about 250° C.;

polarizing all of the pins (VS+, VS/IP−, IP+, RCOMP) by connecting all of the pins (VS+, VS/IP−, IP+, RCOMP) to the electrical ground (GND) through corresponding fourth limiting resistances (RLS);

measuring the voltage of all of the pins (VS+, VS/IP−, IP+, RCOMP) while all of the pins (VS+, VS/IP−, IP+, RCOMP) are connected to the electrical ground (GND); and

diagnosing the presence of a short circuit to the supply voltage (Vcc) in the pin (VS+, VS/IP−, IP+, RCOMP) in which the voltage is higher than a predetermined threshold.

18. The diagnosis method according to claim 17 , wherein the pins (VS+, VS/IP−, IP+, RCOMP) are polarized by being connected to either of the supply voltage (Vcc) and electrical ground (GND) for a third time interval (T 3 ) ranging from about 8 to about 30 msec.

19. The diagnosis method according to claim 17 , wherein the diagnosis method comprises further, after the cooling down of the lambda sensor and before the polarization of all of the pins (VS+, VS/IP−, IP+, RCOMP), steps of:

polarizing none of the pins (VS+, VS/IP−, IP+, RCOMP) by keeping all of the pins (VS+, VS/IP−, IP+, RCOMP) insulated from the electrical ground (GND) and supply voltage (Vcc); measuring the voltage of the pins (VS+, VS/IP−, IP+, RCOMP) while none of the pins (VS+, VS/IP−, IP+, RCOMP) is polarized;

diagnosing the presence of a short circuit to the supply voltage (Vcc) if the voltage of at least one of the pins (VS+, VS/IP−, IP+, RCOMP) is higher than a predetermined threshold; and

diagnosing the presence of a short circuit to the electrical ground (GND) if the voltage of all of the pins (VS+, VS/IP−, IP+, RCOMP) is lower than the predetermined threshold.