System for diagnosing an internal combustion engine

摘要

A system for diagnosing an internal combustion engine having a coolant temperature sensor. A coolant temperature diagnosing circuit is provided which is responsive to the output voltage of the sensor for producing a signal when the voltage exceeds a predetermined range. A fail-safe signal generating circuit is provided which is responsive to engine speed and to produce fail-safe signals dependent on the engine speed so as to prevent stalling of the engine.