In an electronic control for a hybrid vehicle which is driven either by an engine or an electric motor, or both, possible failures in an ignition system and a rotation sensor system are detected during a period in which the engine is rotated by the motor with no fuel supply. Only after no failure is found, the engine is started by supplying fuel and performing ignition. Thus, the fuel supplied to the engine is ignited without fail, and unburned gas release to the atmosphere is surely prevented. Also, good drivability is maintained. In case the invention is applied to a series hybrid vehicle which is driven solely by an electric motor powered by a battery which is charged by an electric generator driven by an engine, the ignition system is diagnosed when the engine is not rotating. After it is determined that there is no failure in the ignition system, the engine is started.