Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – In vehicle wiring
Reexamination Certificate
1999-09-07
2001-04-10
Brown, Glenn W. (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
In vehicle wiring
C324S522000, C324S525000, C324S538000, C324S543000
Reexamination Certificate
active
06215313
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates in general to diagnostic methods for electrical systems which are associated with motor vehicles. More specifically the present invention relates to the use of a switched load within an electrical assembly in order to distinguish between low voltage due to an inadequate power source as compared to low voltage due to a wiring harness problem.
High-current, electronically-controlled assemblies in vehicles require adequate voltage to function properly. An example is a “smart” fuel injection pump which has an on-board electronic control module that controls various solenoids based on various input signals. When the fuel control solenoid is energized, the current draw can range from about 10 amps to 20 amps. If too small a wire is used in the electrical harness, or corrosion increases contact resistance in the harness, the voltage at the fuel injection pump can drop unacceptably low. This can cause fueling problems, timing problems, low power, stalling, and no start. Given today's service environment, this situation can lead to fuel pumps being replaced, when the problem is really with the harness. This results in higher warranty costs and longer service times.
According to the present invention, a diagnostic method is described which can detect unacceptably high harness resistance before symptoms occur.
SUMMARY OF THE INVENTION
One embodiment of the present invention includes providing an internal combustion engine, a first electrical component operable with the engine, a second electrical component operable with the engine, a power supply, an electrical harness for connecting the first electrical component and the second electrical component to the power supply, and a first electronic control module for controlling at least a portion of the engine. The method includes providing electrical power from the power supply through the electrical harness to the first electrical component. A first voltage drop across the first electrical component is measured by the first electronic control module. Electrical power is provided from the power source through the electrical harness in parallel to the first electrical component and to the second electrical component. A second voltage drop across the first electrical component is measured by the first electronic control module. The first voltage drop is compared to the second voltage drop to determine if there is excessive resistance in the electrical harness.
It is an object of the present invention to provide an improved method and apparatus for diagnosing excessive resistance in an electrical harness.
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King Dennis M.
Lewandowski Edward J.
Brown Glenn W.
Cummins Engine Company
Woodard, Emhardt, Naughton, Moriarty & McNett Patent and Tradema
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