CLEVIS 4742594 - Caterpillar

Electronic Controls
Electronic Control Module
The ECM consists of two main components, the control computer (hardware) and the personality module (software). The control computer consists of a microprocessor and electronic circuitry. The personality module contains the engine's operational characteristics. The operating maps influence the engine's performance.Engine Governor
The engine ECM governs engine speed. The engine ECM and the software work together by controlling the amount of fuel that is delivered by the injectors. Desired engine rpm is determined by the throttle position sensor signal and certain sensor readings. Some diagnostic codes may alter engine speed from the desired engine speed. Actual engine rpm is monitored by the engine speed/timing sensor.Fuel Injection
The ECM controls the timing and the amount of fuel that is delivered to the cylinders. This determination is 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. 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 injects more fuel in order to increase the actual engine speed.The ECM controls the amount of fuel that is injected by varying the signals to the injectors. The injectors will inject fuel only if the injector solenoid is energized. The ECM sends a high voltage signal to the solenoid. 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 amount of fuel that is injected.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 calculates the fuel injection timing relative to the top center position of the individual pistons. The ECM also 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.Cold Mode Operation
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 coolant temperature falls below a predetermined value. Cold mode remains active until the engine coolant temperature rises above a predetermined value or until the engine has been running for a predetermined amount of time.FRC Limit
The software inside the engine ECM sets certain limits on the amount of fuel that can be injected. The FRC limit is a limit that is based on the boost pressure. The boost pressure is calculated as the difference in pressure between atmospheric pressure and turbocharger outlet pressure. The FRC limit is used to control the air/fuel ratio for control of emissions. When the engine ECM senses a higher boost pressure, the engine ECM increases the FRC limit. A higher