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Electronic Controls
The 3176B, C-10, C-12, and 3406E Truck Engines electronic system consists of the Electronic 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 3176B, C-10, C-12, and 3406E 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 throttle position sensor to determine the desired engine speed and compares this to the actual engine speed determined through the engine speed/timing 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 temperature sensor, atmospheric pressure sensor, and boost pressure sensor.The ECM determines where top center on cylinder number one is located from the engine Speed/Timing 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 Pos 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 Pos limit (allows more fuel into cylinder). Rated Fuel Pos 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 engine. It provides power and torque curves for a specific engine family and rating. All of these limits are determined at the factory in the Personality Module and cannot be changed.
Example of EUI SystemCustomer Parameters Effect on Engine Governing
A unique feature with Electronic Engines is Customer Specified Parameters. These parameters allow the truck owner to fine tune the ECM for engine operation to accommodate the typical usage and power train of the vehicle.Many of the Customer Parameters provide additional restrictions on the action the ECM will take in response to the drivers' input. For example, the Top Engine Limit is an rpm limit the ECM uses as a cutoff rpm for fuel. The ECM will not fuel the injectors above this rpm.Some parameters are intended to notify the driver of potential engine damage (Engine Monitoring Parameters). Some parameters enhance fuel economy (Vehicle Speed, Cruise Control, Engine/Gear Limits and Idle Shutdown Parameters). Other parameters are provided to enhance the engine installation into the vehicle or provide engine operating information to the truck owner.Engine Monitoring
Caterpillar provides a factory installed Engine Monitoring system. The Caterpillar Engine Monitoring system monitors engine oil pressure, coolant temperature, intake manifold air temperature, and coolant level (optional, OEM installed).The oil pressure, intake manifold air temperature, and coolant temperature sensors are standard on all engines. The Vehicle OEM installs the coolant level sensor and the associated harness. The coolant level sensor is the only optional component of Caterpillar Engine Monitoring. It is selected through a Customer Programmable Parameter.Caterpillar Engine Monitoring can be programmed to four different modes (OFF, , DERATE, and SHUTDOWN). The Coolant Temperature, Oil Pressure and Coolant Level (if selected) Sensors will operate in the Engine Monitoring Mode selected.For example, if DERATE mode was selected, the engine will derate engine power and vehicle speed if the Coolant Temperature, Oil Pressure or Coolant Level (if selected) Sensors detect conditions exceeding acceptable limits.An excessive Intake Manifold Air Temperature will not derate or shut down the engine.Caterpillar Engine Monitoring OFF
If Caterpillar Engine Monitoring is programmed to OFF, the ECM will not flag low oil pressure, high coolant temperature, and low coolant level. No warnings will occur if conditions are exceeded which could cause the ECM to take Engine Monitoring action.The ECM still uses these sensors for normal engine operation, such as the Coolant Temperature Sensor for Cold Mode operation.Caterpillar Engine Monitoring Operation
If the system is programmed to , the ECM causes the Warning Lamp to turn ON, and will also cause the Check Engine Lamp to Flash (because of the Active Diagnostic Code) to indicate a problem has been detected by the Engine Monitoring System. No further ECM or engine action occurs if the ECM is programmed to .Caterpillar Engine Monitoring DERATE Operation
If the system is programmed to DERATE, the ECM begins by flashing or activating the Warning Lamp ON, and the Check Engine Lamp will flash to indicate a problem has been detected by the Engine Monitoring System. If the problem is due to a Low Coolant Level, Low Oil Pressure, High or Very High Intake Manifold Temperature condition, the ECM will cause the Warning Lamp to turn ON and the Check Engine Lamp to flash as mentioned for Mode.When oil pressure becomes Very Low Oil Pressure, coolant level becomes Very Low Coolant Level, or a High or Very High Coolant Temperature are detected, DERATE Mode begins by flashing