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| Illustration 1 | g01688782 |
Left side of the engine (1) Fuel pressure sensor (If equipped) (2) Intake manifold pressure sensor (3) Crankcase pressure sensor (4) Fuel enable valve (5) Fuel temperature sensor (6) Intake manifold air temperature sensor (7) Absolute pressure sensor for Cooled Gas Induction (CGI) system (8) ARD fuel manifold (9) Pilot fuel control solenoid (10) Main fuel control solenoid (11) ECM P1 connector (12) Primary speed/timing sensor (crankshaft) (13) ARD purge air pump (14) Oil pressure sensor (15) Differential pressure sensor for CGI system (16) ECM P2 connector (17) Connectors for the OEM harness to the Diesel Particulate Filter (DPF) (18) ECM | |
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| Illustration 2 | g01689393 |
Right side of the engine (19) Flame Detection temperature sensor (20) Differential pressure sensor for the combustion air (21) Intake valve actuation pressure sensor (22) Spark plug (23) Coolant temperature sensor (24) Flame detection temperature sensor (25) Control group for the CGI system (26) Control group for the combustion air system (27) Flame boundary temperature sensor (28) Temperature sensor for CGI system (29) Ignition coil for the ARD | |
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| Illustration 3 | g01700323 |
ARD fuel manifold (10) Main fuel control solenoid (8) ARD fuel manifold (9) Pilot fuel control solenoid (33) Pilot fuel pressure sensor (34) Main fuel pressure sensor | |
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| Illustration 4 | g01379970 |
Typical DPF (35) Inlet temperature sensor for the DPF (36) Connector for the OEM harness from the engine (37) Sensor group (38) Outlet temperature sensor for the DPF (39) Tubes for the measurement of the differential pressure across the DPF | |
Engine Monitoring
The electronic control system includes engine monitoring. The system monitors engine oil pressure, coolant temperature and coolant level. All On-Highway engines are shipped from the factory with the following sensors: engine oil pressure sensor and coolant temperature sensor. The Original Equipment Manufacturer (OEM) is responsible for providing and installing the coolant level sensor. The coolant level sensor is the only sensor that can be individually selected for engine monitoring. The software for the Engine Control Module (ECM) contains a customer programmable parameter that enables the coolant level sensor. The default factory setting is "NO". The ECM customer programmable parameters have three levels that are for engine monitoring:
- Warning (factory default)
- Engine derate
- Engine shutdown
Warning Mode
Warning mode uses the following sensors: engine oil pressure, coolant temperature and optional coolant level sensor. When a diagnostic code is active, the amber warning lamp will flash and the warning lamp will come on.
Engine Derate and Engine Shutdown
The engine derate and the engine shutdown allows the ECM to alter engine performance in order to avoid damage to the engine. The engine should return to normal conditions once the problem is corrected. When the engine is derated, the check engine lamp and the warning lamp will flash. For the operating conditions that cause these modes, refer to the appropriate section for the sensor.
Electronic Control System Operation
The fuel delivery and injection timing are electronically controlled. In comparison to engines that are controlled mechanically, the electronic control system provides increased control of timing and increased control to the fuel to the air ratio. Injection timing is achieved by precise control of injector firing time, and engine power is controlled by adjusting the firing duration. The ECM energizes the fuel injection solenoid in order to start the injection of fuel. The ECM will de-energize the fuel injection solenoid in order to stop the injection of fuel. Refer to the Systems Operation, "Fuel System" for a complete explanation of the fuel injection process.
The engine uses the following types of electronic components: input, control and output.
An input component is one that sends an electrical signal to the ECM. The signal that is sent varies in either voltage or in frequency when there is a change in some specific system of the vehicle. An example would be the engine speed/timing sensors or the coolant temperature sensor. The ECM sees the input sensor signal as information about the condition, environment, or operation of the vehicle.
An electronic control system component receives the input signals. Electronic circuits that are inside the ECM evaluate the signals. The ECM then supplies electrical energy to the output components of the system, which are in response to predetermined combinations of input signal values.
An output component is one that is operated by the ECM. An output component receives electrical energy from the ECM. The electrical energy is used to perform one of the following functions:
- Perform work. An example would be moving a solenoid plunger. An output component takes an active part in regulating or operating the vehicle.
- An output component can give information or a warning. An example would be a light or an alarm to the operator of the vehicle or other person.
Output components provide the ability to electronically control the engine operation in order to improve the following items: performance, fuel consumption rate and reduced emissions levels. A brief description of the sensors that are used in the electronic control system follows:
Coolant Temperature Engine Monitoring Operation
The amber warning lamp will flash if engine monitoring is programmed to derate the engine. The amber warning lamp will flash if engine monitoring is programmed to shut down the engine. The amber warning lamp will then flash when the associated diagnostic code is active. When the amber warning lamp flashes, the engine is in derate mode.
Atmospheric Pressure
Atmospheric pressure is calculated by using the signal from the absolute pressure sensor for the CGI.
Ambient Air Temperature Sensor
The sensor is used on applications that monitor outside air temperature in order to allow an override of the idle shutdown when the outside air temperature is below a minimum or above a maximum programmed range.
Intake Manifold Pressure Sensor
The intake manifold pressure sensor is an absolute pressure sensor that measures inlet manifold pressure. The difference between the measurement of the inlet manifold pressure and the pressure that is measured by the absolute pressure sensor from the CGI system is called the boost pressure.
Air Inlet Temperature Sensor
This sensor is located in the valve assembly for the CGI system. The sensor measures the air temperature after the air cleaner.
Intake Manifold Air Temperature Sensor
This sensor is located in the air intake manifold. The sensor measures the air temperature at the engine intake manifold.
Coolant Level Sensor
The coolant level sensor is installed by the vehicle OEM. The coolant level sensor indicates when the coolant level is low.
Coolant Temperature Sensor
The engine coolant temperature is measured by an electronic sensor that is mounted on the water temperature regulator housing. The coolant temperature signal is used to modify the amount of the fuel that is delivered to the engine and the engine timing for improvement during cold starts and white smoke cleanup.
Fuel Temperature Sensor
The fuel temperature is monitored in order to adjust the calculations for the fuel rate. The temperature of the fuel is also monitored in order to correct the power of the engine.
Fuel Pressure Sensor (If equipped)
The fuel pressure sensor monitors fuel pressure to the injectors. If low fuel pressure is detected, the engine will log a code and derating of the engine will occur.
Intake Valve Actuation Pressure Sensor
The sensor for the intake valve actuation pressure measures the oil pressure in the external oil rail that is located on the valve cover base. The oil pressure is communicated over the data link and the oil pressure can be displayed by Cat Electronic Technician (ET).
Engine Oil Pressure Sensor
The engine oil pressure sensor is an absolute pressure sensor that measures engine oil pressure in the oil gallery.
Primary Engine Speed/Timing Sensor and Secondary Engine Speed/Timing Sensor
This engine uses two engine speed/timing sensors. The primary engine speed/timing sensor senses the position of the crankshaft gear. The secondary engine speed/timing sensor senses the position of the camshaft gear. Both sensors detect a reference for engine speed and engine timing from a unique pattern on the gear for that sensor. To determine engine speed, the Engine Control Module (ECM) counts the time between pulses that are created by the sensor as the gears rotate.
Under normal operation, the secondary engine speed/timing sensor determines timing for starting purposes. The secondary engine speed/timing sensor is used to determine when the piston in the No. 1 cylinder is at the top of the compression stroke. When the timing has been established, the primary engine speed/timing sensor is then used to determine engine speed.
The engine will start and the engine will run if only one signal from the sensors is present. However, if there is no signal from either engine speed/timing sensor, the engine will stop. The loss of signal from both sensors will prevent the engine from starting.
Accelerator Pedal Position Sensor
The accelerator pedal position sensor is an electronic sensor that is connected to the accelerator pedal. The accelerator pedal position sensor sends a pulse width modulated signal to the ECM.
Vehicle Speed Sensor
The vehicle speed sensor is an electromagnetic pickup that measures vehicle speed. The sensor measures vehicle speed from the rotation of the gear teeth that are in the drive train of the vehicle.
Crankcase Pressure Sensor
The crankcase pressure sensor monitors the pressure of the crankcase. Derating of the engine will occur if the crankcase pressure exceeds the limit.
Intake Temperature Sensor for the Diesel Particulate Filter (DPF)
The intake temperature sensor for the DPF monitors the exhaust gas temperature to the DPF. The sensor is used during regeneration to control the temperature in the DPF.
Differential Pressure Sensor for the DPF
The differential pressure sensor for the DPF monitors the change of pressure. The sensor can trigger a regeneration of the DPF if the pressure exceeds the limit.
Outlet Temperature Sensor for the DPF
The outlet temperature sensor for the DPF monitors the exhaust temperature of the DPF. The sensor can detect an event that might cause a failure of the DPF.
Temperature Sensor for the CGI
This sensor monitors the temperature of the clean gas that is returning from the DPF.
Absolute Pressure Sensor for the CGI
The absolute pressure sensor for the CGI monitors the absolute pressure of the clean gas that is returning from the DPF. The sensor is also used for calculating atmospheric pressure.
Differential Pressure Sensor for the CGI
The differential pressure sensor for the CGI is used to calculate the mass of the clean gas that is returning from the DPF.
Main Fuel Pressure Sensor for the Aftertreatment Regeneration Device (ARD)
The sensor measures the pressure of the fuel in the lines for the main fuel flow.
Pilot Fuel Pressure Sensor for the ARD
The sensor measures the pressure of the fuel in the lines for the pilot fuel flow.
Differential Pressure Sensor for Combustion Air
The differential pressure sensor is used to calculate the mass air flow for the ARD combustion air.
Exhaust Gas Temperature Sensor (Turbocharger Outlet)
The Turbocharger outlet temperature sensor monitors the turbocharger outlet temperature.
Flame Detection Temperature Sensor
The Flame detection temperature sensor detects the flame. The sensor monitors the regeneration system during a regeneration. The sensor also controls the ratio of air to fuel for the ARD combustion system.
Flame Boundary Temperature Sensor
The flame boundary temperature sensor monitors the length of the flame of the ARD during a regeneration. The sensor is used in conjunction with the combustion detection temperature sensor to control the ratio of air to fuel for the ARD system.
Amber Warning Lamp
The amber warning lamp is located on the dashboard of the vehicle. The amber warning lamp can be used as a diagnostic lamp in order to communicate any problems with the operation of the electronic control system.
Note: The amber warning lamp and the red stop lamp are different. For more information about terminology for electronic components, refer to your engine's Troubleshooting Guide.
When a diagnostic fault is detected by the ECM, the amber warning lamp will turn ON. When a diagnostic fault is detected by the ECM, the amber warning lamp will blink at five second intervals. The amber warning lamp should be ON and the amber warning lamp should be flashing diagnostic code 55 whenever the keyswitch is turned ON but the engine is not running. This condition will test whether the lamp is operating correctly.
If the amber warning lamp comes on and the amber warning lamp stays on after the initial start-up, the system has detected a fault. The amber warning lamp or service tools can be used to identify the diagnostic code.
The amber warning lamp is also used to monitor the idle shutdown timer. The amber warning lamp will start to flash at a rapid rate 90 seconds before the programmed idle time is reached. If the clutch pedal indicates a change in position or the service brake pedal indicates a change in position during the final 90 seconds, the idle shutdown timer will be disabled. The idle shutdown timer will then need to be reset.
Engine Control Module (ECM)
The ECM power supply provides electrical power to all engine mounted sensors and actuators. Reverse voltage polarity protection and resistance to vehicle power system voltage swings or surges have been designed into the ECM. The ECM also monitors all input from the sensors. The ECM also provides the correct outputs in order to ensure desired engine operation.
The ECM contains memory in order to store customer specified parameters. The ECM also identifies a factory engine rating. The memory also contains a personality module identification code in order to prevent unauthorized tampering. The memory also contains an identification code in order to prevent switching of engine ratings and other manufacturing information.
The wiring harness provides communication or signal paths to the various sensors. A boost pressure sensor, the data link connector, and the engine/vehicle connectors are examples. The ECM performs many functions. The ECM contains all of the information that regulates engine performance. The ECM contains all of the information for the emission certification. Several examples are listed: engine timing, air/fuel ratio and fuel ratio control maps.
Note: The list that follows contains a portion of the customer specified parameters: engine power rating, vehicle identification number, low gear limit, intermediate gear limit, engine speed limit, gear down protection, Top Engine Limit (TEL), Vehicle Speed Limit (VSL), controls for the vehicle's high gear, Low Cruise Control Set Limit (LCC), High Cruise Control Set Limit (HCC), retarder coast/latch and idle shutdown timer. The customer specified parameters may be secured by customer passwords. An ECM may have all of the programmed parameters or any combination of the programmed parameters. For a brief explanation of each of the customer specified parameters, refer to the Troubleshooting manual for your engine.
The ECM is programmed to run diagnostic tests in order to separate a fault to a specific circuit. Once a fault is detected, the fault can be displayed in several ways on the amber warning lamp. Diagnostic codes can be read by using an electronic service tool. The ECM will log most of the diagnostic codes that are generated during engine operation. The logged codes or the active codes can be read by Cat ET.
Relay Driver Module for the Cooling Fan
The ECM provides a disable function for the cooling fan. If the ECM output is high, the fan is off. The disable function for the cooling fan is for control of the engine's cooling fan. The on/off control is based on the following items: coolant temperature, engine brake mode and engine speed. The on/off control is also based on the air conditioning high pressure switch that is installed by the OEM. All other control of the cooling fan is the responsibility of the OEM.
In order to prevent fan clutch cycling during engine cranking due to low voltage levels, the ECM disables the fan. Because an electrical open circuit is the most likely failure mode, Caterpillar recommends a normally open relay for this circuit.