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| Illustration 1 | g01157677 |
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Top view of engine (1) Intake manifold air temperature sensor (2) Intake manifold pressure sensor (3) Coolant temperature sensor (4) Atmospheric pressure sensor (5) Electronic Control Module (ECM) (6) Fuel pressure sensor (7) Fuel differential pressure switch (8) Fuel temperature sensor | |
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| Illustration 2 | g01157719 |
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Front view (9) Engine oil pressure sensor (10) Secondary speed/timing sensor (11) Primary speed/timing sensor | |
The electronic control system is integrally designed into the engine's fuel system and the engine's air inlet and exhaust system in order to electronically control the fuel delivery. The electronic control system provides better timing control and fuel air ratio control in comparison to conventional mechanical engines. Injection timing is achieved by the precise control of the fuel injectors. Engine speed is controlled by adjusting the injection duration. The Electronic Control Module (ECM) energizes the unit injector solenoids in order to start the injection of fuel. Also, the ECM de-energizes the unit injector solenoids in order to stop the injection of fuel.
Refer to Systems Operation/Testing And Adjusting, "Fuel System" for a complete explanation of the fuel injection process.
The engine uses the following three types of electronic components:
- Input component
- Control component
- Output component
An input component is one that sends an electrical signal to the ECM. The signal that is sent varies in either of the following ways:
- Voltage
- Frequency
- Pulse width
The variation of the signal is in response to a change in some specific system of the engine. Some specific examples of an input component are the engine speed-timing sensors, and the coolant temperature sensor. The ECM interprets the signal from the input component as information about the condition, environment, or operation of the engine.
An ECM receives the input signals from the input components. Electronic circuits inside the control component evaluate the signals from the input components. These electronic circuits also supply electrical energy to the output components of the system. The electrical energy that is supplied to the output components is based on predetermined combinations of input signal values.
An output component is one that is operated by a control module. The output component receives electrical energy from the control group. The output component uses electrical energy to make an adjustment in one of the engine's systems. An output component may also provide information to the operator.
As an example, a moving solenoid plunger will perform work. By performing work, the component has functioned in order to regulate the engine.
As an example, a control panel light or an alarm will provide information to the operator of the engine.
These electronic components provide the ability to electronically control the engine operation. Engines with electronic controls offer the following advantages:
- Improvement in performance
- Improvement in fuel consumption
- Reduction in emissions levels
Various sensors feed data to the ECM. The following sensors are used by the ECM for data:
- Engine coolant temperature
- Engine oil pressure
- Atmospheric pressure
- Primary speed/timing sensor
- Secondary speed/timing sensor
- Fuel temperature
- Fuel pressure
- Intake manifold air pressure
- Intake manifold air temperature
The ECM processes the data. Then, the ECM sends an electronic signal to the fuel injector. The signal will control the amount of fuel that is injected into the cylinder. This will optimize the efficiency and the performance of the engine.
A data link is used for the following items:
- Communicate engine information.
- Communicate with Caterpillar Electronic Technician (ET).
- Calibrate the electronic engine control system.
- Troubleshoot the electronic engine control system.
- Program the electronic engine control system.
The data link is used to communicate engine information to other electronic control systems. Also, the data link can interface with Cat ET.
Cat ET can be used to program the customer specified parameters. The tool is plugged into the data link connector. This allows Cat ET to communicate with the ECM. Also, Cat ET can be used to display the real time values of all the information that is available on the data link. This will help diagnose engine problems.
Electronic Control Module (ECM)
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| Illustration 3 | g01118503 |
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Electronic Control Module (ECM) | |
The engine uses an ECM. The ECM is a microprocessor based device. The ECM is mounted on the top of the front valve cover on the left side of the engine.
The inputs and the outputs to the ECM are designed to withstand short circuits without damage to the control module. The electronic engine control system has the following features that are designed into the system.
- Resistance to radio frequency
- Resistance to electromagnetic interference
The system has passed tests for interference by two-way radios and by switching noise.
The ECM power supply provides electrical power to all engine mounted sensors and actuators. The following precautions have been designed into the ECM.
- Reverse voltage polarity protection
- Swings or surges of the voltage in the power system due to sudden alternator load
The ECM also monitors all sensor inputs and the ECM provides the correct outputs in addition to acting as a power supply. Also, the ECM ensures the desired engine operation.
The ECM is programmed with a selected factory engine rating. The ECM memory contains a personality module identification code. This code is used to avoid unauthorized tampering or switching of personality modules and other pertinent manufacturing information.
The wiring harness provides communications to the following areas:
- ECM
- Various sensors
- Data link connector
- Engine connectors
The ECM is programmed to perform the following functions:
- Diagnostic tests on all inputs
- Diagnostic tests on all outputs
- Identify a faulty circuit.
Once a fault is detected, the fault can be displayed on a diagnostic lamp. The diagnostic code can be read by using Cat ET. A multimeter can be used to check most problems. Also, a multimeter can be used to troubleshoot most problems. The ECM will record most diagnostic codes that are generated during engine operation. These logged codes or intermittent codes can be read by Cat ET.