Abstract: Misfire detection techniques for a hybrid electric vehicle (HEV) including an internal combustion engine and an electric motor involve utilizing a crankshaft speed sensor configured to generate a crankshaft speed signal indicative of a rotational speed of a crankshaft of the engine that is coupled to the electric motor via a flywheel. The techniques also utilize a controller configured to control the electric motor to provide a vibrational response to dampen disturbances to the crankshaft, receive the crankshaft speed signal, selectively modify the crankshaft speed signal to obtain a modified crankshaft speed signal, and detect a misfire of the engine based on the modified crankshaft speed signal and a set of thresholds including at least one of a negative misfire threshold and a positive vibrational response threshold.

Abstract: A method of operating an engine in a vehicle equipped with an evaporative emissions system is described. The engine is configured to perform automatically an engine stop and an engine restart when the vehicle stops moving to increase fuel economy of the vehicle. The method includes the steps of determining if an engine stop is allowed while a diagnostic test of the of the evaporative emissions system is being performed if an engine stop is requested, and preventing the engine stop if the engine stop is not allowed.

Abstract: Rationality diagnostic techniques for an intake oxygen sensor are utilized to detect sensor malfunction. A non-intrusive diagnostic technique includes passively detecting when an exhaust gas recirculation (EGR) valve position crosses low/high position thresholds, whereas an intrusive diagnostic technique includes actively commanding the EGR valve to predetermined low/high positions. During a period after the EGR valve position reaches/crosses at least one of the low/high positions/position thresholds, respectively, maximum and minimum intake oxygen concentration is monitored. When the EGR valve position has crossed both the low/high positions/position thresholds and a difference between the maximum and minimum oxygen concentrations is less than a respective difference threshold, a malfunction of the intake oxygen sensor is detected. A malfunction indicator lamp (MIL) could be set to indicate the malfunction.

Abstract: A method of diagnosing rationality of a humidity sensor output signal determines that the humidity sensor output signal has passed a rationality diagnostic if the output signal is changing sufficiently. If the output signal is not changing sufficiently, the method determines whether it should be changing sufficiently by whether a humidity capacity index determined based on temperature and pressure local to the humidity sensor is changing sufficiently. If the humidity capacity index is changing sufficiently and the humidity sensor output signal is not, the method determines that the humidity sensor output signal has failed a diagnostic check. Upon determining that the humidity sensor output signal has failed the diagnostic check a predetermined number of times, the method determines that the humidity sensor output signal has failed the rationality diagnostic.

Abstract: A method for monitoring an evaporative emissions control (EVAP) system that includes compensating a diagnostic leakage test based on a fuel consumption amount during a test interval is disclosed. The method includes establishing a leak test pressure in the EVAP system, operating the operating the associated valves and pumps such that the EVAP system is expected to be isolated, determining an actual pressure change of the EVAP system, determining an expected pressure change of the EVAP system based on vehicle operating conditions that include the fuel consumption amount, and indicating that a leak is detected if the actual pressure change differs from the expected pressure change by more than a difference threshold.

Abstract: A method for diagnosing a component failure in a saddle-type fuel tank assembly is provided. The method includes a) updating a maximum amount to a subsequent amount of fuel if the subsequent amount of fuel is greater than the maximum amount, b) updating a minimum amount to the subsequent amount of fuel if the subsequent amount of fuel is less than the minimum amount, c) determining a fuel consumption amount, and d) determining that one or more of a first fuel level sender and a second fuel level sender have failed if the difference between the maximum amount and minimum amount is less than a first threshold, and the fuel consumption amount is greater than a second threshold.

Abstract: A method of operating an engine in a vehicle equipped with an evaporative emissions system is described. The engine is configured to perform automatically an engine stop and an engine restart when the vehicle stops moving to increase fuel economy of the vehicle. The method includes the steps of determining if an engine stop is allowed while a diagnostic test of the of the evaporative emissions system is being performed if an engine stop is requested, and preventing the engine stop if the engine stop is not allowed.

Abstract: A method for diagnosing a component failure in a saddle-type fuel tank assembly is provided. The method includes a) updating a maximum amount to a subsequent amount of fuel if the subsequent amount of fuel is greater than the maximum amount, b) updating a minimum amount to the subsequent amount of fuel if the subsequent amount of fuel is less than the minimum amount, c) determining a fuel consumption amount, and d) determining that one or more of a first fuel level sender and a second fuel level sender have failed if the difference between the maximum amount and minimum amount is less than a first threshold, and the fuel consumption amount is greater than a second threshold.