Abstract: A system and method for diagnosing a mechanical failure in an active grille shutter (AGS) system of a vehicle. The method includes receiving at least one mechanical fault condition signal, each of the at least one mechanical fault condition signals being indicative of whether a particular mechanical fault condition was detected in the AGS system. The method also includes receiving a temperature signal indicating a temperature at a location proximate to a grille shutter of the AGS and determining whether to perform an extended diagnostic based on the at least one mechanical fault condition signal and the temperature signal.

Abstract: A method for reducing the engine torque being produced by an internal combustion engine to a desired engine torque through coordinated control of spark retard, cylinder cut-out and air/fuel scheduling. The method is for use with a vehicle including a multi-cylinder internal combustion engine capable of generating torque, each cylinder having an associated fuel injector for providing fuel to the cylinder and an associated spark timing control for providing a spark for combustion of the fuel with fresh air during engine operation. The method includes identifying the desired engine torque to which the engine torque being produced is to be reduced, and determining a first torque reduction to be achieved by defueling at least one of the engine cylinders.

Abstract: A control system which controls engine air/fuel ratio while providing a measurement of efficiency in the catalytic converter coupled to the engine exhaust. A test period is completed when counts in transitions of a feedback variable derived from an exhaust gas oxygen sensor positioned upstream of the converter have reached a preselected count for each of a plurality of inducted air flow ranges. Converter efficiency is determined during the test cycle by comparing an integration of the feedback variable, after band pass filtering and rectification, to an integration of a downstream exhaust gas oxygen sensor after its output is band pass filtered and rectified.