The principles of the system
The electronic diesel control system allows to reduce fuel consumption and emissions of toxic components with exhaust gases (OG), improve the quality of regulation (accuracy, smoothness and speed) and the stability of the idle speed, reduce the rigidity of the diesel engine working process.
The electronic control system for a diesel engine consists of sensors and switches, an electronic control unit and actuators that directly affect the engine systems.
The completeness of the engine management system with sensors and actuators depends on the toxicity standard that the engine meets (for example Euro-3 or Euro-4), vehicle equipment, and vehicle destination.
Information about the operating mode and condition of the engine enters the control system from sensors that convert the controlled (measured) engine parameters into electrical signals that are convenient for processing and transmission in an electronic control system. The signals from the sensors enter the electronic control unit, which, having processed the information received according to the specified algorithms, issues control signals to the actuators based on the driver’s requests and the program in use. The control algorithms implemented by the microprocessor of the electronic unit, at each engine operation mode, produce the optimal (best) fuel consumption and toxicity standards combination of fuel injection parameters (cycle supply and angle of advance of injection) and air charge (boost pressure and degree of exhaust gas recirculation).
The electronic control unit performs operations such as controlling the cyclic supply of fuel, fuel pressure in the battery, controlling the angle of advance of injection, controlling idle speed, the cruise control function, and controlling elements of subsystems to reduce exhaust toxicity.
To simplify troubleshooting, a self-diagnosis function is built into the electronic control unit, which monitors many operating parameters of both the engine itself and all elements of the control system, and when determining a malfunction, it informs the driver by turning on the malfunction indicators on the instrument panel.
The engine control unit
The Cummins ISF engine control unit has a two-block connector. Block “A” (pictured left) is connected to the wiring of the car. Its composition can vary widely depending on the vehicle equipment. On this block, among other things, the control unit receives power and connects to the mass of the car. Block “B” (pictured right) combines engine wiring: sensors and actuators.
Its elemental composition depends on the toxicity standards to which the engine in question meets.
Diagnostic and engine control system indicators
Four indicator lamps are used in the system: a stop lamp, a warning lamp, a maintenance lamp and a start waiting lamp. When the key in the ignition switch is set to position “I” (“turning on the electrical equipment”), the indicator lamps light up and after about 2 seconds they go out, one after the other – this way confirms that the lamps are in working condition and that they connected correctly.
In the event of a high coolant temperature, high air temperature at the intake manifold, low oil pressure or low coolant level, the indicator lights up and blinks after a certain amount of time.
This blinking mode warns that the condition that has arisen lasts for some time and the subsequent state of pressure or temperature has worsened and the engine is close to a stop state (a forced stop of the ECU engine is possible).
Warning Indicator (ICE) warns about the detection of a malfunction and signals the beginning of the display of codes during on-board diagnostics. Turning on the lamp indicates a malfunction of the engine, while the vehicle remains in working condition (the situation is not emergency). Vehicle must be serviced to eliminate the failure.
Stop Indicator (STOP) signals a malfunction of one of the main systems. During on-board diagnostics, the flashing of this lamp corresponds to the fault codes detected by the computer. Turning on the lamp warns of a serious malfunction. In this case, the bus engine should be turned off as soon as possible, as far as safety requirements allow..
Maintenance Indicator (KEY) serves as a warning about the need for maintenance and to alert the driver that the condition of the fluids in the engine is outside the permissible limits.
Start Wait Indicator (START) warns the driver that cold start is required to ensure proper starting.
Note : some vehicle models are equipped with a test switch that allows trouble codes to be read using indicators using a bot diagnostic system.
Along with the Cummins INSITE main diagnostic complex, the diagnosis of the Cummins engine management system is possible with the following instruments:
• Scanmatic 2
According to the applicability table, according to information as of 03.2015, the capabilities of Scanmatik 2 version 2.19.0 in working with the Cummins CM2220 engine control unit (ISF 2.8 / 3.8) for GAZ vehicles are as follows: reading and erasing diagnostic trouble codes, reading current data, controlling actuators, reading the passport of the control unit, configuration, prescribing nozzle codes.
According to the applicability table, the capabilities of Scanmatic 2 version 2.19.0 in working with the Cummins CM2220 engine control unit (ISF 2.8 / 3.8) for PAZ vehicles are as follows: reading and erasing diagnostic trouble codes, reading current data, controlling actuators, reading the control unit passport , prescription of codes of nozzles, adjustment of turns of idling ± 50 rpm.
The current applicability table for Scanmatic 2 can be found here. .
You can purchase the device in the store of the Legion-Avtodata publishing house .
According to the applicability table, according to information as of 03.2015, ScanDoc’s capabilities in working with the Cummins CM2220 engine control unit (ISF 2.8 / 3.8) for GAZ vehicles are as follows: reading and erasing diagnostic trouble codes, reading out the control unit passport, writing injector codes, adjusting idle speed ± 50 rpm.
The current ScanDoc usability chart can be found at .
You can purchase the device in the store of the Legion-Avtodata publishing house – ScanDoc Compact / Scandoc (full version)
Crankshaft position sensor
general information . The crankshaft position sensor is installed in the area of the crankshaft pulley. The principle of operation of the crankshaft position sensor is based on the Hall effect. The sensor determines the position of the crankshaft, and converts this data into signals (rectangular pulses).
Based on these signals, the electronic engine control unit determines the engine speed and adjusts the moment the nozzle starts to open, as well as the duration of its open state and the timing of the fuel injection.
Diagnostics . The sensor has three wires: power, ground and signal wire. The sensor power supply is stabilized, approximately 5 V, and is provided by the engine control unit (terminal B13). The ground contact is also connected to the control unit (contact B14). The sensor signal is applied to the contact B38 of the control unit and is a rectangular pulse with a low level of approximately 0 V and a high level of approximately 5 V.
The main sensor malfunctions lie in three areas:
1) Malfunction of the sensor itself. The Hall effect sensor malfunction manifests itself mainly after warming up the engine – the electronics built into the sensor malfunction due to heating. Pulse gaps occur.
2) Wiring failure. It manifests itself in the form of a complete or partial absence of a sensor signal. It is diagnosed by checking the voltage at the sensor contacts with the ignition on and the connectors on. As well as the continuity of the wiring from the sensor to the control unit with the connectors removed.
3) Malfunction of the rotor of the sensor (driving wheel). It should be noted that the repair of the rotor teeth in case of damage is unacceptable – the rotor must be replaced. Welding changes the magnetic properties of the material and sensor signal failures when passing over a repaired tooth are likely.
The lack of movement of the tachometer needle in case of unsuccessful attempts to start the engine can serve as an indicator of a possible malfunction of the crankshaft position sensor.
Camshaft position sensor
general information . The camshaft position sensor is located on the cylinder head and determines the moment the cylinder No. 1 piston arrives at top dead center on the compression stroke. Based on the sensor signal, the electronic engine control unit determines the sequence of fuel injection for individual cylinders. The principle of operation of the camshaft position sensor is based on the Hall effect.
Diagnostics . The sensor has three wires: power, ground and signal wire. The power supply for the sensor is stabilized, approximately 5 V, and is provided by the engine control unit (terminal B87). The ground contact is also connected to the control unit (contact B63). The sensor signal is applied to the contact B62 of the control unit and is a rectangular pulse with a low level of approximately 0 V and a high level of approximately 5 V.
The main sensor malfunctions lie in three areas:
1) Malfunction of the sensor itself. The Hall effect sensor malfunction manifests itself mainly after warming up the engine – the electronics built into the sensor malfunction due to heating. Pulse gaps occur.
2) Wiring failure, including connectors. It manifests itself in the form of a complete or partial absence of a sensor signal. It is diagnosed by checking the voltage at the sensor contacts with the ignition on and the connectors on. As well as the continuity of the wiring from the sensor to the control unit with the connectors removed.
3) Malfunction of the rotor of the sensor (driving wheel).
Charge pressure sensor and air temperature sensor assembly
general information . The boost pressure sensor is mounted on the intake manifold and is a piezoresistive type sensor. The sensor detects the boost pressure generated by the turbocharger directly in the intake manifold, generating an output signal to the control unit. Charge pressure sensor integrated with charge air temperature sensor.
Diagnostics . The sensor has four wires: power, ground, the signal wire of the boost pressure sensor and the signal wire of the charge air temperature sensor. The power supply for the sensor is stabilized, approximately 5 V, and is provided by the engine control unit (terminal B89). The ground contact is also connected to the control unit (contact B65). The signal of the boost pressure sensor is supplied to the contact B70 of the control unit and represents the voltage, which increases with increasing pressure. The signal from the charge air temperature sensor is applied to terminal B23 of the control unit.
Fuel rail pressure sensor
general information . The fuel pressure sensor is mounted on the fuel accumulator (fuel manifold) and measures the instantaneous values of the fuel pressure in the accumulator with adequate accuracy and speed. Fuel enters the sensor through an opening in the battery and a channel in the sensor housing, which is closed at the end with a diaphragm, thus, fuel under pressure acts on the diaphragm. The sensor element, in turn, converts pressure into an electrical signal. This signal is sent to the electronic engine control unit. Based on the signal from the fuel pressure sensor and depending on the signals of other components of the fuel system, the electronic engine control unit makes the necessary adjustments to the operation of the fuel system (the necessary fuel pressure is created in the battery by controlling the fuel injection pump actuator).
Diagnostics . The sensor has three wires: power, ground and signal wire. The sensor power supply is stabilized, approximately 5 volts, and is provided by the engine control unit (terminal B92). The ground contact is also connected to the control unit (contact B68). The sensor signal is applied to pin B69 of the control unit and represents a voltage that increases with increasing pressure.
Coolant temperature sensor
general information . The coolant temperature sensor is installed in the thermostat housing. It determines the temperature of the engine coolant and transmits a signal to the electronic engine control unit. The sensor is a thermistor. The sensor resistance decreases with increasing coolant temperature. Based on the voltage of the sensor signal, the electronic engine control unit estimates the temperature of the coolant and makes the necessary adjustments to the fuel system.
Diagnostics . The sensor has two wires: ground (terminal B43 of the control unit) and a signal wire that is simultaneously supplying (terminal B46 of the control unit). With the ignition on, terminal No. 2 of the disconnected sensor connector must have a stabilized power supply of approximately 5 volts..
Accelerator pedal position sensor
general information . The accelerator pedal position sensor is necessary to determine the degree to which the driver presses the accelerator pedal. The sensor consists of two potentiometers (variable resistors) having independent circuits (power, signal and ground). Thus, the sensor consists of two channels – No. 1 and No. 2. When you press the accelerator pedal, the resistance of the sensor resistors smoothly change in proportion to the degree of pressing the pedal. The signals of the accelerator pedal position sensor coming to the electronic engine control unit are compared with the programmed characteristic curves (signals from channel No. 1 and No. 2 are also compared with each other, this is necessary to verify the correctness of the readings). The electronic unit, in turn, generates output control signals, on the basis of which the fuel system is controlled (for example, determines the necessary fuel supply).
Oil emergency pressure sensor
General information and diagnostics . The emergency oil pressure sensor is a relay (switching) sensor, the contacts of which close when the oil pressure in the engine lubrication system falls below a certain level. The sensor signal enters the control unit on pin 37B – the sensor closes this circuit to ground. The signal from this sensor when the engine is running (the signal from the crankshaft position sensor is received) the engine control unit gives a command to turn on the STOP fault indicator on the instrument panel. Depending on the implementation of the data exchange system between the instrument cluster and the engine control unit, this command can be transmitted either on a separate circuit (terminal A49) or on the CAN data bus (terminals 14A and 15A).
Atmospheric pressure sensor
general information . The atmospheric pressure sensor detects the current atmospheric pressure and transmits a signal to the engine control unit. This sensor is necessary for the correct operation of the engine at different altitudes..
Diagnostics . The sensor has three wires: power, ground and signal wire. The power supply for the sensor is stabilized, approximately 5 V, and is provided by the engine control unit (terminal B88). The ground contact is also connected to the control unit (contact B64). The sensor signal is applied to terminal B72 of the control unit and represents a voltage that changes with pressure..
High pressure fuel pump (TNVD)
general information . On the high-pressure fuel pump there is an electromagnetic fuel pressure regulator. It maintains the working pressure of the fuel in the battery, depending on the load on the engine. If it is necessary to increase the fuel pressure in the accumulator, the electromagnetic regulator valve closes by a signal from the electronic engine control unit, blocking the high pressure stage from the low pressure line (fuel return). If it is necessary to reduce the fuel pressure in the battery, the electromagnetic regulator valve, on the contrary, opens by a signal from the electronic engine control unit, bypassing part of the fuel to the return line and thereby reducing the fuel pressure in the battery.
general information . The injectors inject fuel into the engine cylinders by a signal from the electronic engine control unit. In the common rail accumulator fuel system, nozzles with an electromagnetic drive are installed.
Turbocharger geometry change drive
general information . On some engine modifications, a variable geometry turbocharger is installed. The drive of the geometry changing system is mounted on the turbocompressor and controls the system of changing the geometry (position of the blades) of the turbocompressor. The electronic engine control unit, receiving data from the crankshaft position sensor, coolant temperature sensor, charge air temperature sensor, boost pressure sensor and atmospheric pressure sensor, which determine the load on the engine and its operating conditions, calculates the optimal position of the blades and sends a signal to the electric motor drive. Thus, the performance of the compressor apparatus of the turbocharger is regulated.
CAN data bus
General information and diagnostics . The CAN data bus (Controller Area Network) is a high-speed serial data line developed by Bosch. It has high noise immunity and error protection. Used to reduce the number of wires when exchanging data in the car. Each of the control units operating on this bus transmits and receives data selectively. The bus is made in a two-wire circuit: CAN-High (H) and CAN-Low (L) channel. The wires are twisted into a twisted pair to improve the noise immunity of the bus. The maximum length of untwisted CAN bus wires must not exceed 40 mm. To ensure the necessary potential difference between the H and L channels, as well as to prevent errors in messages that are possible when signals are reflected, inside the blocks, at the ends of the bus, parallel to the CAN bus terminals are built-in resistors, usually with a nominal value of 120 Ohms. These resistors also help determine the health of the bus wiring on its various branches: measuring the resistance at the corresponding contacts of the removed connectors of the control units operating on the CAN bus, usually should be approximately 120 or 60 Ohms (one 120 Ohm resistor or their parallel connection), depending on the connector of which block is removed (options are possible). Depending on the system implementation, these resistors can be installed inside control units, inside CAN bus intermediate connectors or inside special CAN bus terminators.
An example of building a CAN data bus on a car (various options are possible):
An example of the oscillography of CAN bus signals. The load of the information bus depends on the number of blocks on it and on the amount of information transmitted.
The signals on both channels are always symmetrical to each other and are in antiphase. At rest, on both bus channels (High and Low) should be observed about 2.5 V (corresponds to a logical “1”). The CAN-Low (L) channel signal switches between its high 2.5 V (logical “1”) and low 1.5 V (logical “0”). The CAN-High (H) channel signal switches between its low 2.5 V (logical “1”) and high 3.5 V (logical “0”). Thus, when switching the bus to a logical “0”, the potential difference between the channels is 2 V.
Diagnostics . Possible CAN bus faults lie in three areas:
1) Faulty wiring / connectors (open, short circuit, short to ground or power source).
2) Faulty control units operating on the bus.
3) Crosstalk on CAN-bus wiring (incorrect wiring tracing, wiring is not twisted into a twisted pair).
Important! On GAZelle vehicles with an ISF2.8s3129T Euro-3 engine, a second 120 Ohm CAN data bus terminator is not installed (the first is built into the engine control unit). In this regard, there may be problems with connecting non-original diagnostic equipment to the engine control unit. In the original diagnostic equipment, this terminator is integrated in the scan tool connector parallel to the CAN bus terminals.
Exhaust emission control system
Modern engines must meet the increasingly stringent requirements for the toxicity of their exhaust gases. In order for the engine to meet more stringent environmental requirements, optimize its design, improve the control system, fuel equipment and install additional subsystems to reduce exhaust toxicity. In addition, appropriate fuel must be used..
The following figure shows an approximate graph of the effect of the introduction of toxicity reduction subsystems on the corresponding exhaust parameters (NO X – nitrogen oxides, PM – solid particles (including soot)).
Exhaust gas recirculation (EGR) subsystem
general information . The exhaust gas recirculation (EGR) subsystem is installed on some engine models to achieve Euro-3 toxicity standards, and together with fuel supply correction and Euro-4 standards. On models of engines that comply with Euro-3, it may not be available. EGR Subsystem Reduces Nitrogen Oxide (NO) X ) in atmosphere. Molecular nitrogen is present in the air and under normal conditions it is inert and does not react with oxygen, which is also present in the air. But getting into the combustion chamber of the engine, under the influence of high temperatures, nitrogen is oxidized, resulting in the formation of toxic nitrogen oxides. And the higher the temperature, the more nitrogen oxides occur. The exhaust gas recirculation system sends part of the exhaust gas from the exhaust manifold of the engine through the intake manifold back to the combustion chambers, thereby reducing the combustion temperature of the air-fuel mixture, thereby reducing the formation of nitrogen oxides.
The composition of the EGR subsystem . There are several versions of the EGR subsystem on Cummins engines of the ISF series, depending on which its composition varies. On ISF2.8 engines, the EGR subsystem includes: an EGR valve assembly, a mass air flow sensor, a throttle actuator block.
The EGR valve has an electric actuator, which, at the command of the control unit, opens and closes the recirculation channel by the required amount. The amount of recirculated gases is determined by the mass air flow sensor: a reduction in air flow makes it clear to the control unit that exhaust gases are entering the engine. The throttle servo is mounted on the intake manifold and is required to control the throttle position. The servo drive consists of a DC motor and a throttle position sensor. The throttle servo in the intake system of the diesel engine serves to increase the degree of exhaust gas recirculation by reducing the increased pressure in the intake manifold (this is achieved by covering the throttle), which results in exhaust gas suction into the intake. Throttle control only at low speed.
EGR disadvantages . During operation, the soot contained in the exhaust clogs the recirculation channels and the EGR valve. Thus, sooner or later, the movement of the valve is blocked and it ceases to perform its functions. Typically, the valve locks when it is partially opened, so that recirculated gases are always supplied to the inlet, even when this should not happen. This leads to a violation of the composition of the fuel-air mixture, and as a result, the loss of available power, increase smoke exhaust. This problem is not always solved by flushing the valve: it may fail and require replacement.
Particulate matter in the exhaust also clogs the intake manifold, intake valves. The blockage is so strong that the car can just stand up – air stops coming into the engine. Flushing the intake manifold solves this problem. In addition, because of EGR, engine oil loses its properties faster.
In addition, EGR affects the fuel economy of a diesel engine and leads to a decrease in its thermal efficiency..
As you can see, this subsystem does some harm to the engine, so many car owners remove its elements: all gas recirculation pipes, a recirculation valve, a gas cooler (a heat exchanger in which the heat of recirculated exhaust gases are transferred to the engine cooling system) are removed, and plugs are installed instead of all pipes. But this is not enough: if we just confine ourselves to the physical removal of the EGR subsystem, the control unit that controls its operation will determine the malfunction and inform the driver about this by turning on the indicator on the instrument panel. Therefore, an additional flashing of the engine control unit is required (replacement of the control program – chip tuning), as a result of which the unit will no longer control the EGR elements, and also the working control cards will be replaced with cards that comply with Euro-3 standards.
Particulate Filter (DPF)
General information . Soot of exhaust gases of internal combustion engines, acting as activated carbon, collects harmful substances and is a carcinogen, so inhaling it is extremely undesirable. The Diesel Particulare Filter (DPF) is designed to reduce the amount of soot and other particulate matter in the car’s exhaust. Its function is to capture the solid parts from the exhaust gases and periodically burn them (the so-called regeneration of the particulate filter). The total surface area of the filter element is close to the area of two football fields. As can be seen from the above graph, DPF works in conjunction with EGR: EGR reduces nitrogen oxides, but increases the amount of particulate matter in the exhaust gases, which in turn is solved using DPF.
DPF Subsystem Composition . The DPF subsystem consists of a particulate filter and a differential pressure sensor in the particulate filter. In this composition, this system is installed, for example, on Next Bus buses. The differential pressure sensor in the particulate filter is required to monitor the filter is full. Its readings allow the control unit to determine the moment when regeneration is required. The particulate filter is regenerated by heating it to a temperature of about 700 degrees, as a result of which the solid particles deposited in its channels completely burn out, forming gaseous carbon oxides.
DPF disadvantages . Errors in car operation, poor fuel quality, inappropriate lubricants, use of inappropriate fuel and oil additives, frequent short-distance trips and urban travel patterns often lead to fatal particulate filter malfunctions. Its regeneration becomes impossible. Faced with this problem, the car owner, as in the case of the catalyst, has two ways to solve it: replacing with a new one or removing the seedling. The cost of a new particulate filter is great and often its removal is the only way to return the car to working condition. And in this case, you will also need a flashing of the engine control unit, software disabling the particulate filter.
Selective Catalytic Reduction Converter (SCR)
This subsystem is designed to reduce toxic nitrogen oxides NO X (NO, NO 2 ) in the exhaust. The presence of this subsystem eliminates the need to use EGR to achieve Euro-4 standards, and its use in conjunction with other toxicity reduction systems makes it possible to achieve Euro-5 and Euro-6 standards. As can be seen from the graph, when using this subsystem, the engine operates in modes optimized for reducing particulate matter in exhaust gases (PM-optimized combustion), and in this case, increasing the NO content X in exhaust gases is solved by the SCR subsystem. The principle of operation of the SCR system is to treat the exhaust gas (OG) with an aqueous solution of urea in a reducing catalytic converter. Exhaust Nitrogen Oxides NO X (NO, NO 2 ) after a chemical reaction with an AdBlue reducing agent in the catalyst are converted to nitrogen N 2 and water H 2 O.
Fluid Reduction System (Urea) . The aqueous urea solution used is known under the trademark AdBlue. AdBluе reagent is produced by a special technology from urea with a high degree of purification and demineralized water. The proportion of urea in AdBlue is 32.5%. At this concentration, the reagent has the lowest freezing point of –11 ° C. Any deviation from this concentration leads to an increase in the freezing temperature. The heating of the urea feed system can be carried out both by independent heating elements and from the vehicle cooling system (in this case, the tank heating valve is used). Average reagent consumption varies depending on the engine model and should average about 4% of diesel fuel consumption for engines meeting Euro-4 requirements. The shelf life of the reagent is 1 year.
Precautionary measures . The reagent is not fire hazardous and is classified as safe in accordance with EU Directive 67/548 / EEC. Ingestion of the substance in small quantities is not dangerous. If AdBlue gets into the digestive system, rinse your mouth and drink plenty of water. If the feeling of malaise and discomfort do not go away, you should consult a doctor. With prolonged contact or immersion of body parts in a tank with a substance, skin burns can occur. If possible contact with the substance should use latex gloves. Although the product is not classified as an irritating chemical, direct contact with the eyes can cause short-term discomfort, characterized by lacrimation or conjunctival redness. In case of direct contact with the eyes, rinse immediately with plenty of water and consult a doctor. Reagent spills should be carefully cleaned up to prevent injuries, as the spill surface becomes slippery.
Attention : Avoid liquid spills on vehicle parts. If this happens, the liquid must be washed off with water and remove residues from the surface of the body. If AdBlue dries and crystallizes on the surface, it will cause corrosion..
At high temperatures (approximately 70 ° C – 80 ° C), AdBlue disintegrates, resulting in the formation of ammonia and a possible unpleasant odor. Contamination with foreign substances and bacteria may render AdBlue unsuitable for use. Leaked and crystallized urea leaves white spots that can be cleaned with water and a brush (immediately if possible). AdBlue has a high ability to leak out, therefore it is necessary to protect electrical components and connectors from the ingress of AdBlue. Use only AdBlue manufacturer approved standards in the original packaging. To avoid contamination, do not reuse fused from the AdBlue system..
Attention : the use of water, an aqueous solution of ordinary urea and other liquids other than AdBluе in the neutralization system is not allowed, as this can lead to failure of the neutralization system. Follow AdBlue guidelines. Practice shows that it is precisely various contaminants of the liquid itself that are the most common cause of failure of SCR systems. The liquid is very sensitive to the materials with which it is in contact. These are, first of all, metals: zinc, aluminum, copper, cast iron and brass. Upon contact with these metals, salts are formed which, if released into the catalyst, can damage it.
Catalyst . After urea is fed to the catalyst in the hydrolysis section, urea decomposes into NH ammonia 3 and carbon dioxide CO 2 . In the reducing catalyst, ammonia NH 3 reacts with nitrogen oxides NO X , forming molecular nitrogen N 2 and water H 2 O. For normal operation of the catalyst, it is necessary that it be heated to a temperature of at least 200 ° C. To monitor the temperature of the catalyst and the temperature of the exhaust gas, exhaust gas temperature sensors are used at the inlet and at the outlet of the converter. To monitor the efficiency of the catalyst, a nitrogen oxide concentration sensor is used at the outlet of the converter.
Urea Injection System . Urea is supplied to the exhaust system by the reagent (urea) dosing unit, which includes a pump, dosing and filtration elements. A mixer is used to evenly distribute urea in the exhaust gas stream. A level sensor with an integrated temperature sensor is installed in the urea tank. Urea injection begins when the catalyst reaches operating temperature, provided that a sufficient amount of liquid urea is provided at low ambient temperatures. Urea injection is interrupted when the exhaust gas flow is small (idle) and the exhaust gas temperature is too low.
Attention! Operation of the car without AdBlue reagent leads to a violation of the temperature regime and the failure of the neutralization system.
SCR disadvantages . The presence of this system on the car obliges the driver to maintain the level of urea in the tank, since the operation of the car with an empty tank is prohibited, and the sales infrastructure is still underdeveloped. Certain requirements are also imposed on the quality of the fuel and lubricants used..
The complete set of the engine management system with additional functions depends on the vehicle equipment. These functions are programmed by diagnostic equipment..
Some additional features are described below:
– Constant speed system (cruise control). This function can be activated even on vehicles that were not originally equipped with it. For this, the corresponding control buttons for this system are installed and the program of the control unit changes.
– Speed Limit. This function can be programmed at the factory for vehicles designed to carry children. Disabling this function, if the purpose of the vehicle has changed, is also possible by replacing the control program..
– Increasing the engine idle speed. This function can be activated on vehicles equipped with a speed-keeping system. To do this, the program of the control unit changes, after which the engine speed on a stationary vehicle is set using the cruise control buttons.
– Functions necessary for the operation of the power take-off system: engine control at a constant speed, remote accelerator.
– Motor brake (if equipped).
– Some protective functions necessary for the operation of the engine and other systems: fixing the maximum engine speed, monitoring battery charging, immobilizer, frequency of service, torque limitation (transmission protection), shifting to a lower gear.
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