HARNESS AS-TRANSMISSION 3240843 - Caterpillar

System Operation
The C-10, C-12, 3406E, C-15 and C-16 Truck Engines are designed for electronic control. The injection pump, fuel lines and nozzles used in mechanical engines have been replaced with an electronic unit injector in each cylinder. A solenoid on each injector controls the amount of fuel delivered by the injector. An Engine Control Module (ECM) sends a signal to each injector solenoid to provide complete control of the engine.Electronic Controls
The electronic system consists of the Engine Control Module (ECM), Engine Sensors and Vehicle Interface. The ECM is the computer which controls the engine. The Personality Module in the ECM contains the software which controls how the ECM behaves (the personality module stores the operating maps that define power, torque curves, rpm, etc).Engine Governor
The Electronic Controls on the engine serve as the engine governor. The Electronic Controls determine when and how much fuel to deliver to the cylinders based on the actual and desired conditions at any given time.The governor uses the Accelerator Pedal Position Sensor to determine the desired engine speed and compares this to the actual engine speed determined through the engine Crankshaft Position Sensor. If desired engine speed is greater than the actual engine speed, the governor injects more fuel to increase engine speed. The desired engine speed is typically determined by the position of the accelerator pedal, desired vehicle speed when in cruise control, or desired engine rpm when in PTO control.Timing Considerations
Once the governor has determined how much fuel is required, it must next determine when to inject the fuel. Injection timing is determined by the ECM after considering input from the Coolant Temperature Sensor, Intake Manifold Air Temperature Sensor, Atmospheric Pressure Sensor, and Boost Pressure Sensor.The ECM determines where top center on cylinder number one is located from the engine Camshaft Position Sensor signal. The ECM decides when injection should occur relative to top center and provides the signal to the injector at the desired time. The ECM adjusts timing for best engine performance, fuel economy and white smoke control. Actual or Desired Timing cannot be viewed with an Electronic Service Tool. Fuel Injection
The ECM controls the amount of fuel injected by varying signals to the injectors. The injectors will pump fuel only if the injector solenoid is energized. The ECM sends a high voltage signal to energize the solenoid. By controlling the timing and duration of the high voltage signal, the ECM can control injection timing and the amount of fuel injected.The Personality Module inside the ECM sets certain limits on the amount of fuel that can be injected. FRC Fuel Limit is a limit based on boost pressure to control the air/fuel ratio for emissions control. When the ECM senses a higher boost pressure (more air into cylinder), it increases the FRC Fuel Limit (allows more fuel into cylinder). Rated Fuel Limit is a limit based on the power rating of the engine and rpm. It is similar to the rack stops and torque spring on a mechanically governed