A self-monitoring system for an automotive electronc control system such as an engine control system, an electronic anti-skid control system or electronic automatic transmission control system is adapted to check each segment of the electronic control system in order to detect faulty segments. To detect faulty segments, the self-monitor system checks inputs and outputs of the electronic control system. The checked data is stored in a memory which is not erased when the power supply is turned off. The self-monitoring system is associated with another automotive microcomputer which includes a display unit. The other automotive microcomputer is adapted to display the results of the checking operation of the self-monitoring system in response to a display request manually inputted from a manual unit to display identification of the fault segment and/or error condition thereof. The monitor can also be associated with a fault indicator, such as an LED, which is responsive to detection of error in any of the segments to turn on.