Patent ID: 8694197

Claim:
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.