ROD 6A3105 - Caterpillar

One Electronic Control Module (ECM) is installed on the engine.The ECM controls most of the functions of the engine. The operator interface with the engine control is provided by the Caterpillar Electronic Technician (Cat ET) and by the control panel. For information on Cat ET, refer to Systems Operation/Testing and Adjusting, "Electronic Service Tools".
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Control system block diagram
Electronic Control Module (ECM)
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Typical view of the ECM
(1) J1/P1 ECM connector
(2) J2/P2 ECM connectorThe ECM has two connectors. The J1/P1 connector (1) is a 70-pin connector, while the J2/P2 connector (2) is a 120-pin connector. Each pin provides a connection point for a signal interface for the ECM.Overview of the Electronic Control System
The electronic control system is designed to control the engine operation for optimum performance with minimal emissions.The ECM is the engine control computer for the electronic control system. The ECM provides the capacity for the input/output functions, the control functions, the data link communications, and the computational functionality for the system. This functionality is detailed below:Input/Output Functions
The ECM provides the following input functionality:The ECM relies on several different types of input devices in order to gather information that is related to the current state of engine operation. The ECM receives the status information from the input devices. The information is used to calculate the correct output action that is needed in order to control engine operation. These output actions are based on calculations that are made on cumulative data from other system components, software parameters, and information. The actions taken by the ECM are typically related to desired operation. The ECM utilizes switch inputs, sensor inputs, and data link communications to obtain input information from the engine components.The ECM provides the following output functions:
Power supply control for related components
Controller circuits for engine operation
Communications ports for the communication mediumThe ECM utilizes outputs as power supplies, high side ECM drivers (switch to supply circuits), and low side ECM drivers (switch to ground circuits). The ECM also utilizes data link communications to output command signals to other engine controllers.Control Functions
Control functions are typically commands that are derived internally by the ECM circuitry and software. Control functions are used in