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| Illustration 1 | g03385277 |
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Speedometer/tachometer circuit | |
The components of the speedometer/tachometer circuit are the Power Train Electronic Control Module (ECM), the Engine ECM, the Caterpillar Monitoring System (ECM), the transmission output speed sensor, the primary speed/timing sensor, the secondary speed/timing sensor and the speedometer/tachometer module.
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| Illustration 2 | g01145165 |
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Cab (1) Power Train ECM | |
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| Illustration 3 | g01153775 |
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Right side view of engine (2) Engine ECM | |
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| Illustration 4 | g03392286 |
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Dash panel (3) Caterpillar Monitoring System ECM (behind display) | |
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| Illustration 5 | g00992887 |
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Rear view of transmission (4) Transmission output speed sensor | |
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| Illustration 6 | g00992891 |
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Top view of engine (5) Primary speed/timing sensor | |
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| Illustration 7 | g00992907 |
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Left view of engine (6) Secondary speed/timing sensor | |
With the key start switch in the ON position, 24 V power is supplied from the batteries via:
- Circuit breaker #9 to Power Train ECM (1)
- Circuit breaker #2 to Engine ECM (2)
- Circuit breaker #1 to Caterpillar Monitoring System ECM (3)
Transmission output speed sensor (4), primary speed/timing sensor (5), and secondary speed/timing sensor (6) are magnetic pick-ups. When the gear teeth interrupt the magnetic field, an electrical pulse is generated. This signal is then sent to the relative ECM.
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| Illustration 8 | g03395104 |
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Dash panel (7) Speedometer/tachometer module | |
With the machine moving, transmission output speed sensor (4) generates a signal that is sent to Power Train ECM (1). The machine ground speed is determined by Power Train ECM (1) and sent to Caterpillar Monitoring System ECM (3) via the CAT Data Link. Caterpillar Monitoring System ECM (3) sends a signal to speedometer/tachometer module (7) to display the ground speed.
While the engine is running, primary speed/timing sensor and secondary speed/timing sensor generate a signal that is sent to Engine ECM (2). Engine ECM (2) calculates the engine rpm. Engine ECM (2) sends a signal via CAT Data Link to Caterpillar Monitoring System ECM (3). Caterpillar Monitoring System ECM (3) sends a signal to speedometer/tachometer module (7) to display the engine speed.