Diagnostic device and method of engine exhaust purifying system

Details Diagnostic device and method of engine exhaust purifying system Diagnostic device and method of engine exhaust purifying system

2007-09-11

2007-09-11

Denion, Thomas (Department: 3748)

Power plants

Internal combustion engine with treatment or handling of...

Having sensor or indicator of malfunction, unsafeness, or...

C060S285000, C060S299000, C060S302000

Reexamination Certificate

active

11136533

ABSTRACT:
A diagnostic device and method of an engine exhaust purifying system, which perform active control of an air-fuel ratio and can make diagnosis of air-fuel ratio sensors, catalysts, etc. in the engine exhaust purifying system with high accuracy and reliability while avoiding a worsening of exhaust emissions, an increase of revolution variations, etc. The diagnostic device comprises an exhaust air-fuel ratio control unit for performing control to keep an air-fuel ratio of exhaust gas flowing into a main catalyst near a stoichiometric ratio in accordance with outputs of downstream air-fuel ratio sensors, a rich/lean switching unit for switching over an air-fuel ratio in each of the cylinder groups to be rich or lean, thereby making diagnosis of each downstream air-fuel ratio sensor, a response detecting unit for detecting a response of the downstream air-fuel ratio sensor when the rich/lean switching of the air-fuel ratio in each cylinder group is performed, and a downstream sensor deterioration determining unit for determining a deterioration of the downstream air-fuel ratio sensor based on the detected response.

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