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Electronic Controls
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 is the software for the control computer which contains operating maps that define power and torque curves. The two work together to control engine operation.
Figure 1.1 - Personality ModuleThe ECM governs engine speed (refer to Figure 1.2) by controlling the amount of fuel delivered by the Electronic Unit Injectors. Desired engine rpm is determined by the throttle switch signal and certain sensor readings. Some events may generate a derate that effects desired engine rpm. Actual engine rpm is measured by the Speed/Timing sensor.Fuel Injection
The ECM controls the timing and quantity of fuel injected by varying the signals to the injectors. Fuel is injected ONLY when an injector solenoid is energized by a 105 volt signal from the ECM. By controlling the timing and duration of the 105 volt signal, the ECM controls fuel injection timing and quantity based on engine operating conditions and desired engine rpm.Injection timing depends on engine rpm, load, and other operational factors. The ECM limits engine power and modifies injection timing during Cold Mode to increase startability and reduce white smoke. Cold Mode is activated whenever the engine coolant temperature falls below a predetermined value. It remains active until coolant temperature exceeds a predetermined value or a time limit is exceeded.The ECM has factory programmed limits on the quantity of fuel that can be injected. FRC Fuel Pos is a fuel limit for exhaust smoke control purposes that is based on a maximum allowable fuel-to-air ratio. When the ECM senses a higher Turbocharger Compressor Outlet Pressure (more available air), the FRC Fuel Pos limit is increased to allow more fuel into the cylinder. Rated Fuel Pos is a limit based on the power rating of the engine and is similar to the rack stops and the torque spring on a mechanically governed engine. The Rated Fuel Pos provides power and torque curves for a specific engine family and rating.Programmable Parameters
System Configuration Parameters that affect engine operation are set at the factory and may be changed with an Electronic Service Tool. System Configuration Parameters are stored in the ECM and a record of parameter changes is stored in permanent memory.Several System Configuration Parameters and most Logged Events are protected by Factory Passwords. Factory passwords are calculated on a computer and are available only to Caterpillar dealers. Refer to Section 2: Programming Parameters for details regarding when passwords are needed and how to obtain them.Self-Diagnostics
The ECM has the ability to detect problems with it's inputs and outputs. When a problem is detected, a diagnostic code is generated and an audible or visible alarm may be present at the electronic display module. In most cases the diagnostic code is also stored in the ECM's permanent memory.Current diagnostic codes are referred to as ACTIVE. An Active code indicates a problem currently exists and should always be serviced first. Refer to Section 4: Troubleshooting With A Diagnostic Code for more information.Diagnostic codes stored in memory are called LOGGED. The problem may have been temporary or may have been repaired since the time it was logged. It is important to remember that it is possible to log faults whenever a component is disconnected and the keyswitch is in the ON position. Therefore, logged diagnostic codes do not necessarily mean something needs to be repaired. Logged diagnostic codes may be helpful indicators to determine intermittent problems.In addition to diagnostic codes, the ECM also records EVENTS (such as high coolant temperature or low oil pressure) that have occurred, rather than diagnostics or electronic problems. Refer to Section 3: Troubleshooting Without a Diagnostic Code for more information on event codes.Passwords
The System Configuration Parameter Full Load Setting and most Logged Events are protected by Factory Passwords. Factory Passwords are calculated on a computer system available only to Caterpillar dealers. Refer to Section 2: Programming Parameters for details regarding when passwords are needed and how to obtain them.Electronic Governor Diagram
Figure 1.2 - Electronic GovernorElectrical System Block Diagram
Figure 1.3 - Electrical System Block DiagramSystem Component Diagrams
Figure 1.4 - Engine View - Left SideSystem Component Diagrams
Figure 1.5 - Engine View - Right SideSystem Component Diagrams
Figure 1.6 - Engine View - FrontElectrical Connectors and Functions Electronic Service Tools
Caterpillar Electronic Service Tools are designed to help a service technician obtain and analyze data, and to diagnose existing and potential problems within the electronic system. An Electronic Service Tool is required to perform calibrations and to read or change programmable parameters.There are two Caterpillar Electronic Service Tools that can be used with the engine: Electronic Technician (ET) or the Electronic Control Analyzer Programmer (ECAP). With either ET or ECAP, a Communication Adapter Tool is required to communicate with the Electronic Control Module (ECM). ET is the preferred Electronic Service Tool since it has more capabilities and features, however, ECAP may be used to perform basic troubleshooting procedures.A digital multimeter is required for making voltage and resistance measurements. There are also several required adapter cables, probes, etc, that allow a service technician to perform the measurements and readings needed for diagnosis. These tools are listed in the following tables and diagrams, along with their associated part numbers. Optional Service Tools
Two short jumper wires are needed to check continuity of some wiring harness circuits. The jumper wires are used to short (connect) two adjacent pins or sockets together in a connector. Refer to the Service Tools Diagram for details on how to construct the jumper wires.A long extension wire may be needed to check continuity of some wiring harness circuits. Refer to the Service Tools Diagram for details on how to construct the extension wire.The following list contains service tools that are not required, but may be helpful, to service the engine. Electronic Technician (ET)
The Caterpillar Electronic Technician (ET) is a service tool designed to run on a personal computer. It allows a portable computer