Importance

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Abstract

A diagnostic test apparatus for simulating pin open circuit, pin short to ground and pin shorted-to-voltage fault conditions at each pin of each connector of an engine controller module (ECM). The apparatus includes a parallel port coupled to a demultiplexer circuit. The outputs of the demultiplexer circuit drive a plurality of relay drivers, which each, in turn, control independently a single relay coupled between one particular pin of an ECM connector and its associated circuit line on the vehicle wiring harness, when the apparatus is coupled in line between the ECM connector and the vehicle wiring harness. The apparatus may be controlled by an external computer such that the three above-mentioned fault conditions may be initiated automatically. The parallel port of the apparatus is connected to an external computer, preferably a personal computer, to allow the technician to initiate the fault conditions without requiring the technician to remain inside the vehicle to actuate any switches or other like devices on the apparatus 10. The apparatus thus allows three different fault conditions to be simulated at each pin of the ECM quickly and easily through the use of an external computer. Any fault information recorded by the ECM may be read via a separate serial communications interface between the computer and the ECM and subsequently cleared by the computer. The apparatus thus enables the diagnostics of a vehicle's ECM to be checked quickly and accurately to ensure the ECM recognizes various fault conditions.

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First Claim