Patent ID: 9416735
Filing Date: 2016-08-16
CPC Classification: F02D,Y02T

Claim Text:
1. A diagnostic method for indicating correct operation of a cam profile switching system of an internal combustion engine having a plurality of cylinders with some of the cylinders in a first group and others of the cylinders in a second group, the method comprising: operating the engine with both groups in a first condition of the cam profile switching system; sampling first exhaust gas constituents associated with the first group in said first condition; sampling second exhaust gas constituents associated with the second group in the first condition; determining a first ratio by relating the first exhaust gas constitients to the second exhaust gas constituents; forcing the cam profile switching system of the second group to a second condition of the cam profile switching system while making a corresponding adjustment to fuelling for the second group; sampling third exhaust gas constituents associated with the second group in said second condition; determing a second ratio by relating the first exhaust gas constituents to the third gas constituents; comparing the first and second ratios; and either (i) determining whether the camshaft switching system of the second group has operated correctly based on a difference between the first and second ratios when the difference is less than or equal to 5% or greater than of equal to 15%, or (ii) obtaining an indeterminate result when the difference is between 5% and 15%.