Input/output signal checker for an electronic control unit in an electronically controlled fuel injection system

Claim 1

A checker for an electronic control means, which electronically controls the operation of an internal combustion engine having a plurality of cylinders and as many fuel injection valves provided, respectively, for said cylinders, said checker being adapted to check a plurality of input signals including signals representing numerical quantities of operation parameters of said engine and being supplied to said electronic control means, and a plurality of output signals including signals representing numerical quantities of at least valve opening periods of said fuel injection valves and binary signals representing operation and non-operation of said fuel injection valves and being produced and outputted by said electronic control means in response to said input signals, said checker comprising: a plurality of display means for always displaying information of said input signals and said output signals in respective predetermined modes irrespective of whether said information indicates normality or abnormality, said plurality of display means including an operation sequence display for displaying operation sequence of said fuel injection valves in which they are opened; display hold means connected to at least one of said plurality of display means for having said at least one of said plurality of display means continuously display the information of at least one of said input and output signals representing numerical quantities received thereby; and frequency dividing means connected to said operation sequence display for dividing the frequency of said binary signals representing operation and non-operation of said fuel injection valves in such a predetermined ratio that visual observation of said operation sequence is facilitated and delivering the frequency divided signal to said operation sequence display.