3508B Engine for Caterpillar Built Machines Caterpillar

Electronic Control System Operation

Usage:

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Illustration 1	g00840057
Schematic of the electronic control system

The electronic control system provides improved control of the timing and of the fuel injection over conventional mechanical engines. The electronic control system governs engine speed by precise control of both the timing and of the duration of the fuel injection in order to provide the following benefits:

Improve engine performance.
Minimize fuel consumption.
Reduce emission levels.

The electronic control system consists of the following components:

Electronic control module (ECM)
Electronic display modules
Engine sensors
Output devices
Injector solenoids
Devices for providing feedback
Wiring harnesses

Electronic control module (ECM) - The ECM controls the engine operation. The ECM receives information from engine sensors and devices for providing feedback in order to determine the operating conditions of the engine. The ECM consists of the following components: control computer (hardware), software and input/output circuitry. The control computer consists of a microprocessor and of electronic circuitry. The software (flash file) contains operating maps that define power and torque curves. The software also contains parameters that can be set at the factory in order to fine tune engine performance. The input/output circuitry allows the ECM to transmit information to engine components. The input/output circuitry allows the ECM to receive information from engine components.

Electronic display modules - The engine's ECM communicates with one of two types of display modules. The first module is the Electronic monitoring system (EMS). The second module is the Vital Information Display System (VIDS) or the Vital Information Management System (VIMS). The engine's ECM will receive data via the CAT data link from the display modules. The engine's ECM will send data via the CAT data link to the display modules. The engine's ECM will send filtered data about engine operating conditions to the display modules. The data about engine operating conditions is based on input from the engine sensors and feedback from system components. The display modules will notify the user of engine operating conditions.

Engine sensors - Engine sensors provide feedback to the engine's ECM on critical operating parameters. The ECM uses data from the sensors to monitor engine performance in order to prevent damage to the engine in case of abnormal operating conditions. The ECM can initiate reductions in engine power if abnormal operating conditions exist. The ECM will notify the operator of abnormal operating conditions on the electronic display modules. The engine sensors are listed below. Not all of the following sensors may be used in your application.

Left turbocharger compressor inlet pressure sensor
Right turbocharger compressor inlet pressure sensor
Turbocharger outlet pressure sensor
Coolant temperature sensor
Aftercooler temperature sensor
Inlet manifold temperature sensor
Engine oil pressure sensor
Atmospheric pressure sensor
Crankcase pressure sensor
Right exhaust temperature sensor
Left exhaust temperature sensor
Engine cooling fan pump pressure sensor

Output devices - The ECM will send a signal to output devices in order to cause a specific action. The ECM monitors the voltage or current to a device in order to determine if the circuitry for the device is operating normally. The following devices can be activated by the engine's ECM:

Starter motor magnetic switch
Ether solenoids
Service engine lamp
Engine fan control solenoid
Injector solenoids

Input devices - The engine's ECM receives input from devices that provide a position signal or a position request signal. The ECM uses the information from the input device in order to verify a position of an actuator. The ECM uses the information in order to respond to a command from the operator. The following devices provide an input to the engine's ECM: