Abstract: To enable, with a simple control, a malfunction of a type wherein the output from a knock sensor becomes excessively large to be detected, a knock-sensor malfunction diagnosis device includes a control section configured to determine that knocking has occurred when the magnitude of a knocking vibration frequency component derived from an output signal from a knock sensor exceeds a first threshold value, and diagnose the knock sensor as malfunctioning when a prescribed diagnostic condition wherein knocking cannot occur is satisfied and the magnitude of the knocking vibration frequency component derived from the output signal from the knock sensor exceeds a second threshold value. The control section is further configured to determine that the diagnostic condition is satisfied for a time interval from a time when a predetermined time period has expired after fuel-cutoff has started to a time when the fuel-cutoff ends, during execution of the fuel-cutoff.

Abstract: To enable, with a simple control, a malfunction of a type wherein the output from a knock sensor becomes excessively large to be detected, a knock-sensor malfunction diagnosis device includes a control section configured to determine that knocking has occurred when the magnitude of a knocking vibration frequency component derived from an output signal from a knock sensor exceeds a first threshold value, and diagnose the knock sensor as malfunctioning when a prescribed diagnostic condition wherein knocking cannot occur is satisfied and the magnitude of the knocking vibration frequency component derived from the output signal from the knock sensor exceeds a second threshold value. The control section is further configured to determine that the diagnostic condition is satisfied for a time interval from a time when a predetermined time period has expired after fuel-cutoff has started to a time when the fuel-cutoff ends, during execution of the fuel-cutoff.