TUBE A. 4K8409 - Caterpillar

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Engine stop circuitThe components of the engine stop circuit are the key start switch, the main power relay, and the Power Train Electronic Control Module (Power Train ECM).
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Dash panel (1) Key start switch
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Cab (2) Main power relayWhen key start switch (1) is turned to the OFF position, 24 volt power that energizes main power relay (2) is interrupted. The 24 volt power that is supplied to Power Train ECM (3) via circuit breaker #9 is interrupted, causing the engine to shutdown.Reference: For more information on the engine shutdown systems, refer to Systems Operation, Testing and Adjusting, "Engine Monitoring, Engine shutdown switch and Idle/Timer Fire Suppression Control" for the machine that is being serviced.