5036323 JOHNSON GEAR, FORWARD

Electronic Controls
The electronic system for the engine consists of the ECM, the wiring harness, the engine sensors, the switches, the injection actuation pressure control valve, the unit injector hydraulic pump, the HEUI injectors and the interface for the particular application. The ECM is a computer. The flash file is the software for the computer. The flash file contains the operating maps. The operating maps define the following characteristics of the engine:
Horsepower
Torque curvesThe ECM determines the timing and the amount of fuel that is injected into the cylinders. The calculations are based on the actual conditions and the desired conditions at any given time.The ECM compares the desired engine speed to the actual engine speed in order to calculate an adjustment to the injection timing and to the duration. The actual engine speed is determined via a signal from the engine speed/timing sensor. If the desired engine speed is greater than the actual engine speed, the ECM increases the injection duration in order to increase the actual engine speed.Cold Mode
The ECM limits engine power during cold mode operation and the ECM modifies injection timing during cold mode operation. Cold mode operation provides the following benefits:
Increased cold weather starting capability
Reduced warm-up time
Reduced white smokeCold mode is activated whenever the engine temperature is below 18 °C (64 °F) and the engine has been running less than 20 seconds. Cold mode remains active until the engine temperature rises above 18 °C (64 °F) or until the engine has been running for 14 minutes.Fuel Injection
The ECM controls the amount of fuel that is injected by varying the signals to the injectors. The ECM sends a high voltage signal to the solenoid. The injectors pump fuel only while the injector solenoid is energized. This high voltage signal energizes the solenoid. By controlling the timing and the duration of the high voltage signal, the ECM can control injection timing and the ECM can control the amount of fuel that is injected.The flash file inside the ECM sets certain limits on the amount of fuel that can be injected. The "FRC Fuel Limit" is used to control the air/fuel ratio for control of emissions. The "FRC Fuel Limit" is a limit that is based on the turbocharger outlet pressure. A higher turbocharger outlet pressure indicates that there is more air in the cylinder. When the ECM senses a higher turbocharger outlet pressure, the ECM increases the "FRC Fuel Limit". When the ECM increases the "FRC Fuel Limit", the ECM allows more fuel into the cylinder. The "FRC Fuel Limit" is programmed into the flash file at the factory. The "FRC Fuel Limit" cannot be changed.The "Rated Fuel Limit" is a limit that is based on the power rating of the engine and of the engine speed. The "Rated Fuel Limit" has a function that is similar to the rack stops and the torque spring on a mechanically governed engine. The "Rated Fuel Limit" provides the power curves and the torque curves for a specific engine family and for a specific engine rating. The "Rated Fuel Limit" is programmed into the flash file at the factory. The "Rated Fuel Limit" cannot be changed.Once the ECM determines the amount of fuel that is required, the ECM must determine the timing of the fuel injection. The ECM determines the top center position of each cylinder from the engine speed/timing sensor's signal. The ECM determines when fuel injection occurs relative to the top center position and the ECM provides the signal to the injector at the desired time. The ECM adjusts timing for optimum engine performance, optimum fuel economy, and optimum control of white smoke.Injection Actuation Pressure Control System
The ECM controls fuel injection by controlling oil pressure to the fuel injectors. The pressure of the oil in the high pressure oil manifold is controlled by the ECM through control of the injection actuation pressure control valve. The injection actuation pressure control valve controls the output of the high efficiency pump. The actuator adjusts the pump outlet flow by adjusting the control current that is supplied by the ECM.Starting Aids
An air inlet heater is used by this engine in order to improve the starting of the engine in cold weather conditions. The ECM controls the output of this system. For additional information, refer to the appropriate troubleshooting procedure.Programmable Parameters
Certain parameters that affect the engine operation may be changed with the Caterpillar Electronic Technician (ET). These parameters are stored in the ECM. The parameters may be protected from unauthorized changes by factory passwords, or by customer passwords.Passwords
Several system configuration parameters and most logged events are protected by factory passwords. Factory passwords are available only to Caterpillar dealers. Refer to Troubleshooting, "Factory Passwords" for additional information.