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Gain/amplitude diagnostics of NOx sensors

  • US 8,694,197 B2
  • Filed: 05/26/2011
  • Issued: 04/08/2014
  • Est. Priority Date: 05/26/2011
  • Status: Active Grant
First Claim
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1. A method of diagnosing vehicle NOx sensor faults, comprising the steps of:

  • (a) sensing that an exhaust gas recirculating (EGR) valve is closed and that fuel flow to a vehicle engine is above a predetermined rate using an electronic control unit (ECU) located on a vehicle and programmed to carry out the method steps;

    (b) recording the output received from an NOx sensor relative to an amount of fuel consumption in response to step (a) over a period of time using the ECU;

    (c) calculating the mean of the NOx sensor output relative to fuel consumption recorded over the period of time using the ECU;

    (d) repeating steps (a) and (b) at least once;

    (e) performing a least-squares estimation (LSE) using the ECU for more than one calculated mean based on an expected NOx sensor output;

    (f) generating a NOx sensor gain for the NOx sensor using the ECU based on the LSE; and

    (g) determining whether the NOx sensor gain is above or below predetermined a threshold.

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