Patent ID: 7284365

Claim:
An electric heated catalyst failure diagnostic device comprising: an electric heated catalyst having a heater and being disposed in an engine exhaust system to which electricity is supplied by a power supply; control means, the control means controlling energizing of the heater of the electric heated catalyst; heater abnormality detecting means for detecting first and second heater abnormalities, the detecting means detecting a first abnormality that is an abnormality in a circuit from the power supply to the heater when the control means issues a command to energize the heater, and a second abnormality that is a disconnection abnormality of the heater when the control means issues a command not to energize the heater; and a heater energize command detector for detecting the command from the control means not to energize the heater, wherein the heater abnormality detecting means is activated when the heater energizing command detector detects the command from the control means not to energize the heater.