Steven G Majors

US Patent:

60857323, Jul 11, 2000

Filed:

Jan 25, 1999

Appl. No.:

9/237103

Inventors:

Yue Yun Wang - Columbus IN
Steven W. Majors - Indianapolis IN

International Classification:

F02M 2507

US Classification:

12356812

Abstract:

A system and method for diagnosing EGR system and EGR cooler faults evaluates a temperature signal generated by a sensor at the EGR cooler, such as a coolant or gas temperature sensor. An engine control module includes an on-board EGR diagnosis unit and DSP that reads the EGR cooler temperature signals over a predetermined time period or sample points, and generates a symmetric signal. A discrete fast Fourier transform is applied to the symmetric signal to develop values for the spectral magnitude and phase angle of a primary frequency component of the signal. These values can be compared to respective predetermined threshold values to determine whether a fault condition has occurred in the EGR system or EGR cooler. In an alternative embodiment, the DSP operates in the time domain to determine a signal power value for the change in cooler temperature signal over a predetermined time period. This signal power value can be compared against one or more threshold values to determine the health of the EGR system and cooler.