GAIN/AMPLITUDE DIAGNOSTICS OF NOx SENSORS
First Claim
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1. A method of diagnosing vehicle NOx sensor faults, comprising the steps of:
- (a) recording the output received from an NOx sensor relative to an amount of fuel consumption over a period of time;
(b) calculating the mean of the NOx sensor output relative to fuel consumption recorded over the period of time;
(c) repeating steps (a) and (b) at least once;
(d) performing a least-squares estimation (LSE) for more than one calculated mean based on an expected NOx sensor output;
(e) generating a NOx sensor gain based on the LSE; and
(f) determining whether the NOx sensor gain is above or below predetermined a threshold.
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Abstract
A method that includes in-vehicle systems and practices for determining whether a NOx sensor in an exhaust stream is performing properly. The method uses the gain and/or the offset of the NOx sensor to determine its accuracy.
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Citations
20 Claims
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1. A method of diagnosing vehicle NOx sensor faults, comprising the steps of:
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(a) recording the output received from an NOx sensor relative to an amount of fuel consumption over a period of time; (b) calculating the mean of the NOx sensor output relative to fuel consumption recorded over the period of time; (c) repeating steps (a) and (b) at least once; (d) performing a least-squares estimation (LSE) for more than one calculated mean based on an expected NOx sensor output; (e) generating a NOx sensor gain based on the LSE; and (f) determining whether the NOx sensor gain is above or below predetermined a threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of diagnosing vehicle NOx sensor faults, comprising the steps of:
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(a) determining if one or more predetermined initial conditions exist that relate to vehicle operation; (b) recording output from a NOx sensor when the initial conditions exist; (c) calculating the mean of the recorded output; (d) repeating step (b) and step (c) more than once to generate a plurality of means; (e) performing a least squares estimate (LSE) on the plurality of means based on expected NOx output data values included in a lookup table; (f) comparing the output of the LSE with a maximum gain or a minimum gain for a healthy NOx sensor; and (g) determining if the output of the LSE is greater than or less than the data values included in the lookup table. - View Dependent Claims (13, 14, 15, 16, 17)
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18. A method of diagnosing vehicle NOx faults, comprising the steps of:
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(a) determining that an exhaust gas recirculating (EGR) valve is closed and that the fuel flow to a vehicle engine is above a predetermined threshold; (b) recording the output from an NOx sensor over a predetermined amount period of time while the EGR valve is closed and fuel flow is above the predetermined threshold; (c) calculating the mean value of the recorded output; (d) performing step (b) and step (c) a plurality of times thereby generating a plurality of mean values; (e) calculating a least squares estimate (LSE) of the plurality of mean values with respect to expected output from a healthy NOx sensor; (f) using the LSE to determine if an offset exists; and (g) monitoring output from the NOx sensor to determine if the output rises above the high-gain threshold or falls below the low gain threshold. - View Dependent Claims (19, 20)
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Specification