Engine control apparatus with mode changeover function

This application is based on Application No. 2002-029135, filed in Japan on Feb. 6, 2002, the contents of which are hereby incorporated by reference. An engine control apparatus with a mode changeover function for transition to a fault diagnosis mode and fault decision display without using dedicated fault diagnosis input/output unit includes plural input terminals connected to plural input units (), respectively, and plural output terminals connected to plural corresponding display devices (), respectively. The apparatus is designed to fetch input information from the input units () to thereby drive the display devices () and change over control modes in response to external input information. A removable short-circuit line () is provided for forming a short-circuit selectively between a predetermined one of the plural output terminals and a predetermined one of the plural input terminals. A mode changeover decision unit decides the control mode changeover when the short-circuit is formed.