The control system consists of the following components:
- Electronic Control Module (ECM)
- Software (flash file)
- Wiring
- Sensors
- Actuators
The following information provides a general description of the control system. Refer to Systems Operation, Testing, and Adjusting for detailed information about the control system.
Electronic Control Circuit Diagram
 | |
| Illustration 1 | g03570461 |
Electronic control circuit diagram for the C4.4 engine with an EMCP 4.2 control panel | |
 | |
| Illustration 2 | g03573496 |
Electronic control circuit diagram for the C4.4 engine with an MCS control panel | |
Block Diagram
Refer to Illustration 3 for a block diagram of the control system.
 | |
| Illustration 3 | g03573658 |
Block diagram for the engine (1) Air cleaner (2) Air inlet temperature sensor (3) Exhaust gas temperature sensor (if equipped) (4) Turbocharger (5) Air-to-air aftercooler (6) Engine (7) Coolant temperature sensor (8) Primary speed/timing sensor (9) Fuel injectors (10) Return fuel cooler (11) Sea water pressure sensor (if equipped) (12) Return fuel pressure relief valve (13) Secondary speed/timing sensor (14) High-pressure fuel pump/transfer pump/fuel temperature sensor (15) Fuel rail pressure sensor (16) Pre-filter oil pressure sensor (if equipped) (17) Post filter oil pressure sensor (18) Coolant pressure sensor (19) Oil temperature sensor (if equipped) (20) Fuel leakage detection sensor (if equipped) (21) ECM (22) Electric fuel lift pump (23) Post-primary fuel filter pressure sensor (24) Pre-primary fuel filter pressure sensor (25) Primary fuel filter (26) Intake manifold pressure sensor (27) Intake manifold air temperature sensor (28) Transfer pump inlet regulator (29) Secondary fuel filter (30) Fuel tank (31) Post-secondary fuel filter pressure sensor (32) Pre-secondary fuel filter pressure sensor | |
System Operation
Engine Governor
The ECM governs the engine. The ECM determines the timing, the injection pressure, and the amount of fuel that is delivered to each cylinder. These factors are based on the actual conditions and on the desired conditions at any given time during starting and operation.
The governor uses the throttle signal to determine the desired engine speed. The governor compares the desired engine speed to the actual engine speed. The actual engine speed is determined through interpretation of the signals that are received by the ECM from the engine speed/timing sensors. If the desired engine speed is greater than the actual engine speed, the governor injects more fuel in order to increase engine speed.
 | |
| Illustration 4 | g02414657 |
Engine speed control | |
Timing Considerations
Once the governor has determined the amount of fuel that is required, the governor must determine the timing of the fuel injection. Fuel injection timing is determined by the ECM after considering input from the following components:
- Coolant temperature sensor
- Intake manifold air temperature sensor
- Intake manifold pressure sensor
The ECM adjusts timing for optimum engine performance and for economic fuel usage. Actual timing and desired timing cannot be viewed with the electronic service tool. The ECM determines the location of top center of the number one cylinder from the signals that are provided by the engine speed/timing sensors. The ECM determines when injection should occur relative to the top center position. The ECM then provides the signal to the injector at the desired time.
Fuel Injection
The ECM sends a high voltage signal to the injector solenoids in order to energize the solenoids. By controlling the timing and the duration of the high voltage signal, the ECM can control the following aspects of injection:
- Injection timing
- Fuel delivery
The flash file inside the ECM establishes certain limits on the amount of fuel that can be injected. The FRC Fuel Limit is a limit that is based on the intake manifold pressure. The FRC Fuel Limit is used to control the air/fuel ratio for control of emissions. When the ECM senses a higher intake manifold pressure, the ECM increases the FRC Fuel Limit. A higher intake manifold pressure indicates that there is more air in the cylinder. When the ECM increases the FRC Fuel Limit, the ECM allows more fuel into the cylinder.
The Rated Fuel Limit is a limit that is based on the power rating of the engine and on the engine rpm. The Rated Fuel Limit is like the rack stops and the torque spring on a mechanically governed engine. The Rated Fuel Limit provides the power curves and the torque curves for a specific engine family and a specific engine rating. All of these limits are determined at the factory. These limits cannot be changed.
ECM Lifetime Totals
The ECM maintains total data of the engine for the following parameters:
- "Total Operating Hours"
- "Engine Lifetime Hours"
- "Total Idle Time"
- "Total Idle Fuel"
- "Total Fuel"
- "Total Max Fuel"
- "Engine Starts"
The "Total Operating Hours" is the operating hours of the engine. The operating hours do not include the time when the ECM is powered but the engine is not running.
The "Engine Lifetime Hours" is the number of hours when electrical power has been applied to the engine. These hours will include the time when the ECM is powered but the engine is not running.
"Total Idle Time" and "Total Idle Fuel" can include operating time when the engine is not operating under a load.
Fuel Information can be displayed in US gallons or in liters.
"Total Fuel" is the total amount of fuel that is consumed by the engine during operation.
"Total Max Fuel" is the maximum amount of fuel that could have been consumed by the engine during operation.
"Engine Starts" is the total number of times when the engine has been started.
Programmable Parameters
Certain parameters that affect engine operation may be changed with the electronic service tool. The parameters are stored in the ECM, and the parameters are protected from unauthorized changes by passwords. These parameters are either system configuration parameters or customer parameters.
System configuration parameters are set at the factory. System configuration parameters affect emissions or power ratings within an engine family. Factory passwords must be obtained and factory passwords must be used to change the system configuration parameters.
Customer parameters are variable. Customer parameters can affect the following characteristics of the engine within the limits that are set by the factory and the monitoring system:
- Rpm ratings
- Power ratings
Customer passwords may be required to change customer specified parameters.
Some of the parameters may affect engine operation in an unusual way. An operator might not expect this type of effect. Without adequate training, these parameters may lead to power complaints or performance complaints even though the performance of the engine is to the specification.
Refer to Troubleshooting, "Configuration Parameters" for additional information on this subject.
Passwords
System configuration parameters are protected by factory passwords. Factory passwords are calculated on a computer system that is available only to Caterpillar dealers. Since factory passwords contain alphabetic characters, only the electronic service tool may change system configuration parameters. System configuration parameters affect the power rating family or emissions.
Customer parameters can be protected by customer passwords. The customer passwords are programmed by the customer. Factory passwords can be used to change customer passwords if customer passwords are lost.
Refer to Troubleshooting, "Factory Passwords" for additional information on this subject.