Patent ID: 8014916

Claim:
An internal-combustion-engine ignition diagnosis apparatus that is provided in an internal combustion engine having an ignition device that performs operation of generating a spark discharge for igniting a fuel supplied into a combustion chamber of the internal combustion engine and a high voltage device that generates a high voltage for generating the spark discharge and applies the high voltage to the ignition device, and that diagnoses a condition of the spark discharge generated by the ignition device, the internal-combustion-engine ignition diagnosis apparatus comprising: a biasing device that generates a biasing voltage whose polarity is opposite to that of the high voltage and applies the biasing voltage to the ignition device; a signal extraction device that extracts a signal generated due to application of the biasing voltage; a first duration setting unit that sets a first detection duration in which the extracted signal is processed; a second duration setting unit that sets a second detection duration in which the extracted signal is processed; and a diagnosis unit that diagnoses a condition of the spark discharge, based on the signal in the first detection duration and the second detection duration, wherein the first duration setting unit sets the first detection duration in a predetermined duration including a time instant when the spark discharge is generated, wherein the second duration setting unit sets the second detection duration after the first detection duration, and wherein the diagnosis unit determines normality of the spark discharge, based on a signal state in the second detection duration, and regardless of the signal state in the second detection duration, determines abnormality of the spark discharge, based on a signal state in the first detection duration.