IGNITION CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINE

The ECU (40) outputs an ignition signal Si to an ignition apparatus (30) through an ignition communication line (Li), and outputs a discharge waveform control signal Sc with a binary value of "1" through a waveform control communication line (Lc). The ignition apparatus (30) performs the closing operation of the ignition switching element (60), in a period during which the ignition signal Si is input. In an input period of the discharge waveform control signal Sc after the input stop of the ignition signal Si, the ignition apparatus (30) controls the electric current flowing through a primary coil (52), by the opening-closing operation of a control switching element (80). When the voltage of the waveform control communication line Lc still is a binary "1" during an output stop period of the discharge waveform control signal Sc, the ECU (40) determines that the waveform control communication line (Lc) is abnormal, and executes a fail-safe process.