Abstract: An internal combustion engine having a crankshaft rotatable within an engine block of the engine and at least one camshaft driven by the crankshaft. The crankshaft is fixed to a crankshaft wheel having a plurality of crankshaft wheel marks and at least one crankshaft position indicia. The camshaft is fixed to a camshaft wheel having a predetermined pattern of camshaft wheel marks. A crankshaft sensor is fixed to the engine block for producing a crankshaft signal in response to detection of the crankshaft position indicia. A camshaft sensor is fixed to the engine block for producing camshaft signals in response to detection of the camshaft wheel marks. Rotation of the crankshaft generates a pattern comprising the crankshaft signal and the camshaft signals. A processor compares the generated pattern to a stored reference pattern for determining from such comparison the position of the crankshaft within the engine block.

Abstract: Apparatus, method and system are provided for monitoring catalytic converter efficiency in treating exhaust gas from an internal combustion engine. The air/fuel ratio fed to the engine is perturbed on a cylinder-to-cylinder basis above and below a mean or average air/fuel ratio. The signal from an exhaust gas exposed to the exhaust gas sensor downstream of the converter for the perturbation interval is compared to the signal for a non-perturbation interval. A signal is generated when the comparison indicates catalytic converter efficiency below a minimum acceptable level. The comparison may be carried out by comparing the difference in the mean value of the EGO sensor output signal for the perturbation and non-perturbation intervals to a preselected and stored reference value corresponding to the minimum acceptable efficiency. The efficiency monitoring test system may be incorporated into fuel control means for controlling air/fuel ratio during normal engine operation.