Methods and systems for operating an exhaust gas oxygen sensor based on water contact at the sensor

Abstract

An engine method comprising:indicating water at an exhaust oxygen sensor (126) positioned in an engine exhaust passage (48) based on a sensor parameter of the exhaust oxygen sensor (126) during operation of the exhaust oxygen sensor (126) in a variable voltage mode where a reference voltage is adjusted from a lower, first voltage to a higher, second voltage;adjusting one or more of sensor operation and engine operation based on the indicating of water, wherein the sensor parameter includes a pumping current of the exhaust oxygen sensor (126) when the exhaust oxygen sensor (126) is operated at the second voltage;andindicating water at the exhaust oxygen sensor (126) in response to the pumping current of the exhaust oxygen sensor (126) exceeding a threshold current, and wherein adjusting the operation of the exhaust oxygen sensor (126) includes operating the exhaust oxygen sensor (126) in variable voltage mode until the pumping current falls below the threshold current;

Claims

[1] Engine process comprising: Indicating water at an exhaust oxygen sensor (126) positioned in an engine exhaust passage (48) based on a sensor parameter of the exhaust oxygen sensor (126) during operation of the exhaust oxygen sensor (126) in a variable voltage mode where a reference voltage is adjusted from a lower, first voltage to a higher, second voltage; adjusting one or more of sensor operation and engine operation based on the indication of water, wherein the sensor parameter includes a pumping current of the exhaust oxygen sensor (126) when the exhaust oxygen sensor (126) is operated at the second voltage; and Indicating water at the exhaust oxygen sensor (126) in response to the pumping current of the exhaust oxygen sensor (126) exceeding a threshold current, and wherein adjusting the operation of the exhaust oxygen sensor (126) includes operating the exhaust oxygen sensor (126) in variable voltage mode until the pumping current falls below the threshold current. [2] The engine method of claim 1, wherein the sensor parameter includes a change in pumping current when the exhaust oxygen sensor (126) is modulated between the first voltage and the second voltage. [3] The engine method of claim 1, further comprising indicating no water at the exhaust oxygen sensor (126) once the pumping current falls below the threshold current, and wherein adjusting operation of the exhaust oxygen sensor (126) includes transitioning the exhaust oxygen sensor (126) from the variable voltage mode to a non-variable voltage mode where the reference voltage is adjusted to and maintained at the first voltage. [4] The engine method of claim 1, wherein the threshold current is based on an output pumping current, the output pumping current being determined based on an output of the exhaust oxygen sensor (126) while operating in the variable voltage mode when no water is detected at the exhaust oxygen sensor (126). [5] The engine method of claim 1, wherein adjusting one or more of the sensor operation and the engine operation includes reducing an exhaust gas recirculation (EGR) flow in response to the pumping current of the exhaust gas oxygen sensor (126) exceeding the threshold current. [6] The engine method of the preceding claim, wherein adjusting one or more of the sensor operation and the engine operation further includes increasing the EGR flow in response to the pumping current of the exhaust gas oxygen sensor (126) falling below the threshold current. [7] The engine method of the preceding claim, wherein reducing the EGR flow includes decreasing an opening of an EGR valve (142) positioned in an EGR passage (140) and increasing the EGR flow includes increasing the opening of the EGR valve (142). [8] System for an engine (10), comprising: an exhaust gas oxygen sensor (126) coupled to an engine exhaust passage (48) of the engine (10); and a controller (12) including computer-readable instructions stored in a non-volatile memory for: during operation of the exhaust oxygen sensor (126) in a reference mode, wherein a reference voltage of the exhaust oxygen sensor (126) is maintained at a lower, first voltage, detecting a water splash event based on a first pumping current of the exhaust oxygen sensor (126) falling below a first threshold current; and transition the exhaust oxygen sensor (126) to a variable voltage mode (VVs), wherein the reference voltage is modulated between the first voltage and a higher, second voltage, and maintain operation in the variable voltage mode until a second pumping current of the exhaust oxygen sensor (126) falls below a second threshold current, wherein the second pumping current is generated at one or more of the first voltage and the second voltage. [9] The system of the preceding claim, wherein the first threshold current is based on a first output of the exhaust oxygen sensor (126) in the reference mode when no water is present at the exhaust oxygen sensor (126), and the second threshold current is based on a second output of the exhaust oxygen sensor (126) in the variable voltage mode when water is present at the exhaust oxygen sensor (126). [10] The system of claim 9, wherein the second threshold current is higher than the first threshold current. [11] The system of claim 9, wherein the controller (12) includes instructions for estimating an air-fuel ratio based on the first output of the exhaust gas oxygen sensor (126) when the exhaust gas oxygen sensor (126) is operated in the reference mode. [12] The system of claim 9, wherein the controller (12) includes instructions for estimating an ambient humidity based on the first output of the exhaust oxygen sensor (126) when the exhaust oxygen sensor (126) is operating in variable voltage mode.

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