Apparatus and method for diagnosing erratic pressure sensor operation in a fuel system of an internal combustion engine

A fuel system includes a pair of electronically controllable high pressure fuel pumps operable to supply high pressure fuel from a lower pressure fuel source to a high pressure fuel accumulator having a pressure sensor associated therewith. The fuel collection chamber feeds an electronically controllable valve operable to dispense the high pressure fuel to a fuel distribution unit supplying fuel to a number of fuel injectors. A control computer is provided for controlling the high pressure fuel pump and valve in response to requested fueling, engine speed and fuel pressure provided by the pressure sensor. The accumulator pressure signal is processed in accordance with the present invention for diagnosing erratic pressure sensor failures. The control computer is operable to compute error pressure values based on differences between peak accumulator pressure values and a target pressure value, and compute pressure error variance values based on subsets of the pressure error values. A fault code is logged and a limp home fueling algorithm is executed if a predefined number of variance values exceed a variance threshold.