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International DT466 – ENGINE SYSTEMS – Electronic Control System – Operation and Function

The Electronic Control Module (ECM) monitors and controls engine performance to ensure maximum performance and adherence to emissions standards.
The ECM has four primary functions:
1. Provides Reference Voltage (VREF)
2. Conditions input signals
3. Processes and stores control strategies
4. Controls actuators

1. Voltage reference(VREF)
The ECM supplies a 5 volt VREF signal to input sensors in the electronic control system.
By comparing the 5 volt VREF signal sent to the sensors with their respective returned signals, the ECM determines
pressures, positions, and other variables important to engine and vehicle functions.
The ECM supplies two independent circuits for VREF:
• VREF A supplies 5 volts to engine sensors
• VREF B supplies 5 volts to vehicle sensors

2. Signal conditioner
The signal conditioner in the internal microprocessor converts analog signals to digital signals, squares up
sine wave signals, or amplifies low intensity signals to a level that the ECM microprocessor can process.
3. Microprocessor
The ECM microprocessor stores operating instructions (control strategies) and value tables (calibration parameters). The ECM compares stored instructions and values with conditioned input values to determine the correct operating strategy for all engine operations.
Continuous calculations in the ECM occur at two different levels or speeds: Foreground and Background.
• Foreground calculations are much faster than background calculations and are normally more critical for engine         operation. Engine speed control is an example.
• Background calculations are normally variables that change at slower rates. Engine temperature is an example.
Diagnostic Trouble Codes (DTCs) are generated by the microprocessor, if inputs or conditions do not comply with expected values.
Diagnostic strategies are also programmed into the ECM. Some strategies monitor inputs continuously and command the necessary outputs to achieve the correct performance of the engine.