Electronic control unit (controller). Electronic control unit (ECU) - the brain of your car What is an engine control unit

A modern car is not just four wheels and an engine. This is a smartphone on wheels. The operation of all systems of a modern car is controlled by a huge number of different sensors. This information is then analyzed by a special computer and other electronic stuffing. The more expensive the car, the more it has a variety of electronic options. All this "orchestra" is controlled by one small box - this is the ECU. What it is? This is an electronic control unit. We will talk about him today.

ECU in a modern car

The first step is to start with terms. The ECU is the "brains" of the car or the electronic control unit. Many people know him as a controller. It really is the brain of the machine. Without this block, all other elements and mechanisms simply turn into lifeless trash, a huge amount of plastic, wires and microprocessors.

The electronic unit receives data from sensors. Then the information is processed according to special algorithms. Then he sends special commands to the actuators. There is an ECU even in models from AvtoVAZ. There are also sensors - for example, oxygen, coolant temperature, speed. What can we say about modern foreign cars.

This is the electronic control unit of the ECU. In simple words, this is a smart device that keeps under control all the processes that take place in cars every second. Up to a thousand different signals are processed per second.

What does the controller control?

You can list several main sensors from which information is collected. These are the temperature of the engine, the environment, the lambda probe, the fuel level and idling. Also in many cars there are sensors for ABS, brake pad wear and other sensors responsible for safety.

Separate elements control the speed of movement, the position of the electronic gas pedal. There is a crankshaft position sensor. The ECU also controls the operation of the cooling system, climate control. The unit monitors the correct operation of the brake system.

Naturally, this is not the whole list of sensors. This is a kind of standard set that is found on any more or less modern car. Approximately such a set of functions has the VAZ-2170 ECU. We talked about sensors, but we also need to talk about actuators.

This is the throttle position regulator, injector, ignition system. The ECU also controls the distribution phases, the combustion temperature of the mixture and is able to maintain it. The unit analyzes the composition of the exhaust gases. It regulates the operation of lighting, controls power windows, all heating, the operation of robotic and automatic transmissions.

This is just the minimum of what the average ECU can do. What it is, we already know, so let's go further - it will be interesting. On machines of a higher class, there are much more all sorts of sensors and devices.

In fact, the ECU is a small-sized unit that keeps the operation of the entire car under vigilant control. Each system is controlled by this computer. Far from the automotive world, people and novice drivers think that the computer in appearance is a laptop (after all, is it a computer?). But that's not the case at all. The control unit is manufactured in a slightly different form factor.

What does an ECU look like and what is it?

The control unit is made in a variety of cases. Often these are plastic or aluminum bases. For example, the VAZ-2172 ECU is made in a plastic case. On most foreign cars, the body is metal. The material for the most part depends on the location of the block. So, if on models from AvtoVAZ the unit is installed in the cabin, then it is made of plastic. If it was installed under the hood, it would be made of metal.

But the case is not the whole computer. There is an electronic board inside the case. This is the ECU. What it is, we already know about. Two connectors are brought out of the board - this is the so-called CAN bus. Wires from all sensors and actuators are connected to these connectors. It should be noted that some units are also equipped with a connector for updating the firmware, as well as an OBD-II diagnostic output. Like any computer, this one also sometimes “bugs”. Also, failures occur in the sensors. Using the diagnostic connector, you can read the error codes of the VAZ ECU and then it will be easier to repair the car. You no longer need to search for breakdowns manually.

ECU microcircuits are subject to rather strong heating. Therefore, their bodies have ribs. The latter act as radiators, removing excess heat. If you take and look at the dismantled block, then in appearance the block is a small box measuring 15 by 10 cm, its thickness is no more than a centimeter.

ECU from the inside

If you open the block, you can see a fairly large board. Inexperienced car owners, and generally inexperienced computer users, will be able to confuse it with a computer motherboard. We will not understand its device thoroughly, but let's go through the main nodes in passing.

Let's focus on the memory of the computer. What it is? There are several types of memory. PROM is a programmable constant, where the developers have put the necessary algorithms for the operation of the engine and other systems. RAM - RAM, which is necessary to work with intermediate information. It is processed in real time. EEPROM is an electronic, reprogrammable memory. Used to store temporary data.

Software

Functional software is the most important. After all, it is due to it that information from sensors is read and analyzed, and commands are sent to actuators.

The modules control the received data for errors, if any were found. The software tries to correct errors if possible. If the error cannot be corrected, then the on-board computer displays Check Engine, etc. You do not need to remember all the computer errors. Their decoding is different for all types of cars. For example, on the Lada Priore, code P0353 indicates an open circuit in the ignition coil of the 3rd cylinder.

Where is the ECU located?

In the cabin, the unit can be found under the panel. In models from AvtoVAZ, it is located near the heater radiator. On foreign business-level cars, the ECU can be found under the rear seat. Some manufacturers are trying to install the controller in the trunk. Putting the ECU under the hood is not the best solution.

After all, there the block is affected by rain, snow and other factors. Often in the engine compartment, this device can be found near the battery or under the safety block. It is easy to find - even an ordinary car owner without special skills can find it. You just need to disassemble the dashboard a little or find a block under the hood. Outwardly, this is a box from which two wiring harnesses depart. But it’s not worth it to repair the computer yourself without special knowledge. It is better to entrust this work to professionals.

Dismantling

Removing the control box is very easy. It is enough to unscrew the retaining bolts and disconnect the cables. Naturally, before these works, you should remove the negative terminal from the battery. On some car models, it is necessary to disassemble the dashboard. Often the block is located on the side of the stove or under the glove compartment.

Finding out if a block is working is very simple. Half the time, the car simply won't start. It is also possible that all systems will be blocked, all locks will open, and the like. In other cases, engine malfunctions may occur. So, on some machines, revolutions can float, failures occur. The engine may not start at all. Errors are burning that cannot be removed using the software. It should be noted that the ECU is a fairly reliable node. Therefore, if you do not specifically “drown” it, the unit will work for a long time and properly.

How do breakdowns happen if the unit is reliable? It's simple - a short circuit or moisture on the board is enough. Also, the ECU does not like physical impacts and corrosion.

Repair, replacement

It is difficult to say whether to repair the computer or replace it. Sometimes the controller burns out completely, so much so that it can no longer be repaired. A new block needs to be installed. And this is not so cheap - the average price is from 15 to 40 thousand rubles.

But if the error can be eliminated by replacing one or two microcircuits, then repair is advisable. If corrosion has eaten a track on the board, this can also be restored.

Conclusion

Now novice drivers know what an ECU is in a car, where the unit is located and what it is for. This is useful information that will help all car owners. Now on sale there are special diagnostic devices with which you can independently determine the breakdown of a car.

An integral part of modern cars is considered electronic engine control unit. It is designed to receive information from a set of sensors and its subsequent processing. The processed information receives a certain algorithm, with the help of which a control action takes place on various motor systems.

Electronic engine control unit (ECU) - how does it work?

The use of this device effectively optimizes parameters such as power, fuel consumption, torque, the content of harmful substances in exhaust gases, and others. The design of the electronic unit includes two main types of support. With the help of hardware, various electronic components are put into operation, led by a microprocessor.

The information coming from the sensor is converted into digital signals. For this, a special converter is used. The software includes functional and control computing modules. They process the received signals and send them to control the actuators. In addition, output signals are generated that can be corrected up to a complete stop.

If necessary, the electric control unit can be reprogrammed. This happens with significant changes in the design of the engine, for example, when tuning it. For data exchange, a special bus is used, with the help of which all control units are combined into a single system.

Repair of engine control units - how to handle it yourself?

An electronic diesel engine control system is installed on almost all modern engines of this type with various fuel injection systems. Such electronic control is intended mainly for regulating and optimizing their work. Thus, the efficient functioning of the entire fuel system, turbocharging, intake and exhaust systems, as well as cooling and exhaust gas recirculation systems is ensured.

All electronic control consists of the main unit, input sensors, as well as actuators of engine systems. Often, many motorists may be faced with the need to resolve such an issue as repairing an electronic engine control unit. The possibility of carrying out such repairs independently is considered relevant.

From the very beginning it is important to find out exactly the name of the block, in the event that the necessary output parameters are missing. The device is mainly used ECU, translated as "electronic control unit". With its help, work is carried out in accordance with the input signals of the sensors, which create output signals that control the actuators.

Causes of breakdowns and repair of the engine control unit

Repair of electronic engine control units may be necessary in the absence of uninterrupted electrical power. In this case, it is easy to assume an internal malfunction that requires mandatory repair. The reasons may be:

• lack of data exchange with the scanner and the message of incorrect parameters;
• The control lamp "Check" does not light up when the ignition is on;
• with one of the faulty elements, an error fixation is issued.

In addition, the engine may work incorrectly, with deviations, but information about this is not issued.

Timely repair of engine control units will help to avoid many serious problems. In modern cars, so many systems are closed to this device that in the event of any malfunction of the unit, the operation of the entire mechanism or its individual components and assemblies can completely stop. So, we find the culprit of this discussion, the location of which can be specified in the operation manual for the car, and we see that this is entirely electronics. How to find a problem and solve it in such a variety of circuits, transistors and other small elements?

There can be at least two reasons why the ECU gives errors or does not respond to the readings of any sensors: the conductor has become unusable or the firmware has gone astray. It is impossible to restore the firmware yourself if you do not specialize in this area, so they will only help you at the dealership. But you can easily check the electrical parameters if you have a multimeter at hand. To know which wires to check for a breakdown, you need to master reading the circuit of your ECU.

Modern digital technologies allow the use of a wide range of control functions in the car. Many parameters affecting its operation can be taken into account simultaneously, so that different systems can be controlled with maximum efficiency. The electronic control unit (ECU) receives electrical signals from sensors or generators in the expected range of values, evaluates them and then calculates the starting signals for actuators (drives). The control program is stored in a special memory, and the microprocessor is responsible for the implementation of this program.

Fig.57 Electronic control unit. 1 - connector, 2 - low power driver stages, 3 - switching power supply (SMPS), 4 - CAN interface (data bus interface), 5 - microprocessor memory unit, 6 - high power driver stages, 7 - input and output circuits .

Operating conditions

The ECU is subject to very high requirements in relation to the following factors:

• ambient temperature (during normal operation should be between -40 - +85°С for commercial vehicles and -40 - +70°С for cars);
• to influence from materials such as oil and fuel, etc.;
• to influence to humidity of environment;
• have mechanical strength, for example, in the presence of vibrations during engine operation.

At the same time, very high requirements apply to electromagnetic compatibility and protection against high-frequency interference.

Device and design

The ECU (Fig. 57) is placed in a metal case and is connected to sensors, actuators and a power source through a multi-pin connector (1). The components of the electronic system for direct control of the actuators are located in the ECU housing in such a way as to ensure good heat dissipation to the environment.

If the ECU is installed directly on the engine, then heat is removed through a cooler built into the ECU housing, in which fuel constantly flows (only for commercial vehicles). Most ECU components are made using SMD (Surface-Mounted Device) technology. Conventional wiring is only used in some batteries and connectors, so compact low-mass designs can be applied here.

Fig. 58 Signal processing in the electronic control unit of the computer. H - high level L - low level. FEPROM - programmable memory (read-only memory), EEPROM - read-only memory, RAM - random access memory, A / D-ADC, CAN - data bus.

Data processing

Input signals

Along with peripheral actuators, sensors represent the interface between the vehicle and the ECU, which is the data processing unit.

The ECU receives electrical signals from sensors through the vehicle's wiring and connectors. These signals can be of the following types:

Fig.59 Pulse width modulation signals. a - constant period, b - signal duration.

Signal conditioning

To limit the voltage of the input signals to the maximum allowable value, protective circuits are used in the ECU. Through the use of filtering devices, the superimposed interference signals are in most cases separated from the useful signals, which, if necessary, are then amplified to an acceptable level of the input signal of the computer.

The formation of signals in sensors can be complete or partial, depending on the level of their integration.

Signal processing

The ECU is the control center of the system, which is responsible for the sequence of functional operations. Control functions with and without feedback are performed in the microprocessor. Input signals generated by sensors, generators with expected parameter values ​​and interfaces of other systems serve as input coordinates. They are further checked for validity in the computer. Output signals are calculated using programs, characteristics and programmable matrices. The microprocessor is synchronized by a crystal oscillator.

Fig.60 Scheme for calculating the fuel supply in the electronic control unit.
Ignition key in position A (start),
Ignition key in position B (driving modes).

• Programmable (rewritable memory). For its operation, the microprocessor requires a program that is stored in programmable memory (Read Only Memory - ROM, or EPROM / FEPROM).

This memory also contains special data (individual data, characteristic and programmable matrices). This is fixed data and cannot be changed while driving.

Many options that require different data recording make it necessary to limit the number of ECU types for car manufacturers. The entire programmable memory area (Flash EPROPM, or FEPROM) can be programmed (program and model-specific data) when the vehicle rolls off the assembly line (EoL-End of Line programming). It is also possible to store in memory a number of data options (that is, for different countries), which are then selected by EoL programming.

• RAM. Random access memory (RAM) is required to store changing data such as numerical values ​​of signals. RAM requires constant electrical power to function properly. When the ignition or start switch is turned off, the ECU turns off and therefore loses all memory (so-called “evaporative” memory). The adaptive values ​​of the quantities, i.e. those that are “learned” by the system during operation and that relate to the operation of the engine operating modes, in this case must be “learned” again after the computer is switched on again.

Data that should not be lost (such as immobilizer codes and fault code data) must be permanently stored in read-only memory (EEPROM). In this case, the data in the permanent memory is not lost even if the battery is disconnected.

• Application Specific Integrated Circuit (ASIC). The increasing complexity of ECU functions means that the computing power of microprocessors is not sufficient. The solution is to use modules with specialized integrated circuits (ASIC - Application-Specific integrated Circuit) - the development potential of the ECU and, since they are equipped with increased RAM (extra RAM) and advanced input and output blocks, they can generate and transmit pulse-width modulation signals.
• Current control block. The ECU is equipped with a tracking circuit, which is built into an application-specific integrated circuit (ASIC). The microprocessor and monitoring unit monitor each other and, as soon as a malfunction is detected, either of them can turn off the fuel supply independently of the other.

Output signals

Using its output signals, the microprocessor starts the driving stages. The output signals are usually powerful enough to directly drive actuators or relays. The driving stages are protected against short circuits to ground or battery, as well as against destruction from electrical overload. Such malfunctions, together with open circuits or sensor malfunctions, are detected by the driver stage controller, and this information is transmitted to the microprocessor.

Switching signals

These signals are used to turn actuators on and off, for example, the electric fan of the engine cooling system.

Pulse-width modulation signals (PWM signals)

The output digital signals may be in the form of pulse width modulation signals. These are rectangular signals with a constant period, but variable in time (fig. 59), which can be used to start electromagnetic drives, for example, an exhaust gas recirculation valve.

Data transfer within the ECU

In order for the microprocessor to function properly, peripheral components must be able to communicate with it. This is the case when using an address bus or data bus, through which the microprocessor provides, for example, the address of the random access memory (RAM) that should be currently available. The data bus is then used to transfer the corresponding data. Previous automotive systems were satisfied with an 8-bit topology with a data bus that included eight lines, which together could transfer 256 data at the same time. The 16-bit address bus that was commonly used in such systems could transfer data to 65536 addresses.
Modern, more complex systems require 16 bits or even 32 bits for the data bus. In order to keep system components in operation, multiplexing (repeated) transmission can be used for address buses (data buses). That is, data and addresses are sent on the same transmission lines, but are shifted from one another in time.

Built-in diagnostics

• Current control of sensors. In order to make sure that there is a normal supply voltage and that the output signal of the sensor is within acceptable limits (for example, for a temperature sensor this range is between -40 and +150 ° C), the operation of the sensors is monitored by built-in diagnostic devices.

The signals of the most important sensors are duplicated as far as possible. This means that another similar signal may be used in the event of a malfunction, or two or three selections may be made.

• Determination of faults. This can be done within a special area for monitoring the operation of sensors. In the case of systems with feedback programs (e.g. pressure control), it is also possible to diagnose deviations in the given control range.
  The signal path can be considered incorrect if the fault is present for more than a given period of time. If once this period has been exceeded, then the malfunction is stored in the memory of the computer along with the parameters of the conditions under which it happened (for example, coolant temperature, engine speed, etc.).

For many faults, the sensor can be rechecked if the signal path is determined to be traceable as having no fault in the time period under consideration.

• Reaction in the event of a malfunction. If the output signal of the sensor is out of range, it switches to the default value of the signal. This procedure is used for the following input signals: battery voltage; temperature of the coolant, intake air, engine oil; boost pressure; atmospheric pressure and intake airflow.

In the event of a violation of functions important for traffic, a switch is made to substitute functions that allow the driver to drive, for example, to a car service. If one of the potentiometers in the accelerator pedal position module is faulty, then the second potentiometer signals can be used for calculations, provided they are plausible, or engine operation can be switched to a constant low speed mode.

The principle of operation of the electronic control system

The ECU evaluates the signals received from external sensors and sets limits on the permissible voltage level.

Using these inputs and the stored programmable matrices, the microprocessor calculates the duration and advance angle (start time) of the injection and converts these data into performance signals as a function of time, which are then adapted to the movement of the pistons. Given the high dynamic loads of the motor and the high speed, high computing power of the microprocessor is required to meet the requirements for calculation accuracy. The output signals are used to drive driver stages that provide the appropriate power to all actuators (e.g. solenoid valves), including drivers for engine functions such as EGR and bypassing the turbocharger turbine, as well as auxiliary functions such as glow plug relays. and air conditioning. The driver stages are protected against destruction and damage due to short circuits and electrical overload. Signals about such malfunctions as an open circuit are transmitted back to the microprocessor.

The diagnostic functions of the solenoid driver stages also determine the alarm code for the fault. In addition, a certain number of output signals are sent to other vehicle systems via the interface. The ECU also monitors the operation of the entire fuel supply system within the scope of the safety concept.

Working mode management

To ensure an optimal combustion process in the engine, the ECU must perform an appropriate calculation of the amount of fuel supply for each operating mode. The block diagram for calculating the amount of fuel supply is shown in fig. 60.

Starting fuel supply

Starting fuel delivery is calculated as a function of coolant temperature and engine speed. The ECU provides an output signal for starting power from the moment the ignition is turned on (position “A” in Fig. 60) and glow plugs, until the minimum engine speed is reached. The driver cannot influence the amount of starting feed.

Vehicle traffic control

While the vehicle is moving, the amount of fuel injected (delivery amount) is calculated as a function of the accelerator pedal position (accelerator pedal position sensor) and engine speed (ignition switch in position “B” in Fig. 60) using the multivariable vehicle control characteristic . This control provides an optimal match between the actions of the driver and the choice of engine power.

Regulation of the minimum frequency of rotation of idling

At minimum idle, fuel consumption is determined mainly by the engine's mechanical efficiency and engine speed.
In today's dense traffic with frequent stops, the main share of fuel consumption falls on the minimum idling. This therefore means that, on the one hand, the minimum idle speed must be kept as low as possible, and on the other hand, regardless of the load (air conditioning on, automatic transmission selector position, maneuvering during power steering, etc.) , it should never drop below a certain minimum when the engine jerks or even stops.

In order to set the required speed, the minimum idle speed controller changes the fuel supply until its measured value becomes equal to the required one. The required speed and control characteristics are determined by the position of the selector (in an automatic transmission) and the temperature of the engine coolant (from the signal from the coolant temperature sensor).

In addition to taking into account the influence of the moment of resistance from the application of an external external load, one should also take into account the moments of internal friction, which must be compensated by the minimum idle speed control system. These changes are minimal, but are constantly made throughout the life of the vehicle.

Engine Smoothness Control

Due to manufacturing tolerances and depending on engine wear, there are differences in the amount of torque generated by the individual cylinders. This is especially evident at the minimum idle speed, when it leads to uneven, jerky, engine operation. The engine smoothness control system monitors changes in its operation at each moment in time when a flash occurs in the cylinders, and compares the operation of the cylinders with each other. The amount of fuel injected into each cylinder is then controlled depending on the measured difference in speed between the individual cylinders, so that the contribution of each cylinder to the creation of engine torque is the same.

Vehicle speed control (Cruise Control)

The cruise control system controller allows you to control the car at a given constant speed.

It maintains the speed of the car according to the value selected by the driver using a switch located on the dashboard.

During regulation, the amount of injected fuel is increased or decreased until the actual speed is equal to the set speed. The regulation process is automatically terminated as soon as the driver presses the clutch or brake pedal. If the driver presses the accelerator pedal, the vehicle can only be accelerated up to the speed set by the “Cruise Control” system. As soon as the accelerator pedal is released, the controller starts adjusting the speed again according to the previous setting. If the "Cruise Control" system has been deactivated, the driver only needs to press the enable button to reselect the previously set speed.

It is also possible to set the desired speed in steps using the “cruise control” switch.

Fuel limit control

There are a number of reasons why it is not desirable to always inject the maximum amount of fuel.

Such reasons may be:

• high emission of harmful substances from exhaust gas;
• high emission of soot particles due to excess fuel supply;
• mechanical overload at maximum torque or with a large excess of rotational speed;
• thermal overload as a result of increased temperature of the coolant, oil or exhaust gases of the turbocharger.

The fuel injection limit is based on a number of inputs such as mass air flow, engine speed and coolant temperature.

Rice. 61 Active vibration damping. 1 - hard depressing of the accelerator pedal, 2 - speed characteristic without active vibration damping, 3 - speed characteristic with active vibration damping.

Damping speed fluctuations

When the accelerator pedal is abruptly depressed or released, a rapid change in the amount of fuel injected occurs and, as a result, a rapid change in engine torque. Such abrupt changes in engine load lead to the formation of “elastic” vibrations and, as a result, to fluctuations in the engine crankshaft speed (Fig. 61).

Oscillation damping reduces such periodic oscillations in speed by correspondingly changing the amount of fuel injected at the same frequency as the frequency of oscillation of the speed, that is, less fuel is injected at the moment of increasing the speed, and more when it decreases.

Height compensation

Atmospheric pressure affects the regulation of boost pressure and is the engine's torque limiter. When using an atmospheric pressure sensor, its value can be measured by the ECU, so that when operating at high altitudes, the fuel cycling can be reduced and, accordingly, the exhaust smoke of the engine is reduced.

Cylinder shutdown

Instead of injecting very small doses of fuel to reduce torque at high idle and light loads, a method of shutting off part of the cylinders can be applied. For example, half of the injectors can be disabled (fuel systems with unit injectors, individual high pressure fuel pumps and Common Rail), while the remaining injectors will supply more fuel with greater accuracy in dosing.

In the processes of turning on and off the cylinders, algorithms of a special program ensure a smooth transition of modes, as a result of which torque fluctuations do not occur.

Engine stop

The operation of a diesel engine is based on the principle of self-ignition. This means that the engine can only be stopped if the fuel supply is cut off.

Engines with an electronic control system are stopped by the ECU signal “cyclic supply - zero” (No start signal is given to the supply control solenoid valves). There are also a number of backup ways to stop the engine. Fuel systems with unit injectors and individual injection pumps are characterized by high safety. In other words, an unintended injection can only happen once. Consequently, the diesel engine stops when the solenoid valves for fuel control are turned off.

Information exchange

Communication between the engine ECU and other vehicle ECUs is carried out through the network controller - the CAN data bus system. This system is used to transmit desired and set parameter values, operating data and information about the status of systems, which is required for error detection and effective control (see section “Data transmission to other systems”).

External influence on the amount of cyclic fuel supply

The cyclic feed rate is externally influenced by other ECUs (e.g. ABS, TCS), which inform the engine ECU whether to change the engine torque (and therefore the feed rate) and, if so, by how much.

Electronic immobilizer

One of the anti-theft measures is an immobilizer ECU, which can be installed to prevent unauthorized starting of the engine.

In this case, the driver can use the remote control signal to inform the ECU that he intends to use the vehicle. The immobilizer ECU then tells the engine ECU that the fuel inhibit can be lifted and the engine can start.

Air conditioner

When the ambient temperature is high, the air conditioner cools the air inside the car to the desired level by using the refrigeration compressor.

Depending on the type of engine and the characteristics of the driving modes, the power spent on the compressor drive can reach 30% of the engine power.

The engine's electronic control system quickly turns off the compressor as soon as the driver presses the accelerator pedal hard (in other words, it increases the engine torque dramatically). This allows the engine to get full power to ensure acceleration of the car and has little effect on the temperature in the car.

Glow plug control unit

The engine ECU provides the glow plug control unit with information about the need to turn on the glow plugs and the duration of the heating period. The glow plug control unit monitors the heating process and reports any malfunctions to the engine ECU for diagnostic purposes.

Rice. 62 Start signal sequence in the high pressure fuel solenoid valves. 1 - phase of the starting current (breakaway current), 2 - determination of the injection advance angle (moment of the start of injection), 3 - current holding phase, 4 - abrupt power off.

High pressure solenoid valves in fuel systems with unit injectors and individual injection pumps: Starting signals

Triggering signals for high pressure solenoid valves place stringent demands on driver stages
The need to maintain small tolerances and repeatability of cyclic feeds with high accuracy requires that the current pulses of the current characteristic have steep leading and trailing edges.

When forming starting signals, current control is used, in which the formation process is divided into a phase of increase (rise) of the breakaway current and a phase of its retention. Between these two phases, a constant voltage is applied for a short period of time in order to determine when the solenoid valve closes. The current control must be so precise that the injection pump or injector always ensures the repeatability of the fuel injection process in each operating mode. The current control is also responsible for reducing energy losses in the ECU and solenoid valves. In order to ensure a controlled and fast opening of the solenoid valve at the end of the injection process, the energy stored in the valve is instantly released by applying a high voltage to its terminals.

The microprocessor is responsible for calculating the individual starting phases. This process is carried out with the help of a so-called logic matrix, characterized by high computational capabilities, which fulfill this requirement by generating two digital start signals in real time - a “MODE” signal and an “ON” signal. In turn, these trigger signals cause the driver stages to generate the required sequence of the current trigger process (Fig. 62).

Fuel injection timing control (injection advance angle)

The start of fuel injection is defined as the point in time (angle of c.p.v.) at which the high pressure solenoid valve closes and pressure begins to increase in the high pressure chamber of the injection pump. As soon as the pressure exceeds the pressure of the beginning of the rise of the nozzle needle, the latter opens and the fuel injection process begins. The calculation of the actual fuel supply during injection is carried out in the period between the start of the supply and the removal of the start signal from the solenoid valve. This period is called the duration of fuel injection.

The fuel injection advance angle, i.e. the moment the injection starts, has a significant effect on engine power, fuel consumption, exhaust emissions and noise. The injection advance angle setpoint, which is a function of engine speed and fuel delivery, is stored in a multi-parameter map in the ECU. Its value can be adjusted depending on the temperature of the engine coolant.

Due to manufacturing tolerances and changes in the operation of the high pressure fuel solenoid valves during their service life, there may be slight differences in the timing of activation of the solenoid valves on a given engine. This leads to differences in the timing of the start of fuel injection in individual injection pumps of different cylinders.

In order to comply with the requirements of the standards for the emission of harmful substances from the exhaust gas and to achieve good results in the smooth operation of the engine, it is necessary to compensate for these violations by means of an appropriate control algorithm.

Considering the direct correlation between the geometric feed start and the fuel injection start described above, it is sufficient to take into account accurate data on the start of the geometric feed to ensure accurate control of the injection advance angle.

To accurately determine the moment of the start of the geometric fuel supply, an electronic calculation of the strength of the current passing through the solenoid valve winding is used, and in this case, the use of an additional sensor (for example, an injector needle lift sensor) is not required. The start signal to the high pressure solenoid valve is generated by a DC voltage near the time when the valve should close. The magnetic induction that occurs when the solenoid valve closes gives the characteristic of the current in the valve winding an individual value. It is evaluated by the ECU and deviations from the expected closing timing setpoint for each solenoid valve are stored in memory to be used as compensation data for the subsequent fuel injection process.

Data transfer to other systems

Systems overview

Modern car electronic control systems include the following functions:

• electronic engine control and the injection pump itself;
• electronic shift control in the transmission;
• anti-lock braking system (ABS);
• traction control system (TCS);
• electronic stability program (ESP);
• brake torque control system (MSR);
• electronic immobilizers (EWS);
• on-board computers, etc.

The use of these functions makes it necessary to provide communication between individual ECUs through networking. The exchange of information between different control systems reduces the total number of sensors, while activating the use of the potential inherent in individual systems. Communication system interfaces that have been specifically designed for automotive applications can be divided into two categories: conventional interfaces; serial interfaces, i.e. CAN (Controller Area Network).

Rice. 63 Scheme of normal data transmission. 1 - transmission control unit, 2 - instrument cluster, 3 - engine control unit, 4 - ABS / ESP systems control unit.

Normal data transfer

In conventional automotive data systems, one communication channel is provided for each signal (Fig. 63). Binary signals can only be transmitted as one of two possible - "1" or "0" (high or low level, respectively). An example here would be a car air conditioner compressor that is either on (On) or off (Off).

Binary “ON/OFF” signals can be used to transmit constantly changing data, such as accelerator pedal position sensor signals.

The ever-increasing flow of data between different on-board electronic systems means that conventional interfaces can no longer provide satisfactory data transfer characteristics. The complexity of electrical wiring and the size of the associated connectors are already very difficult to manage today, while the requirements for communication between computers are increasing .

In some car models, each ECU is networked with up to 30 different components - providing channels that are almost impossible to achieve with conventional wiring at an affordable price.

Serial communication (CAN)

Communication problems with multiple wires and conventional interfaces can be solved by using data buses. CAN is a data bus system specially designed for automotive applications. The data is broadcast as a serial transmission, that is, the information elements are transmitted one after the other over one line (one communication channel). ECUs can receive and transmit data provided they are equipped with a CAN serial interface.

Areas of use

There are four main areas of application for the CAN system in the vehicle, as shown below.

• multiplex transmission. Multiplexing (repeated) data transmission is convenient for use with programs that perform control in closed or open circuits in on-board electronics systems, including comfort and convenience systems such as climate control, central locking and seat adjustment.

The baud rate is typically between 10 kbps and 125 kbps (low speed CAN).

• Mobile communication programs. In the field of mobile communications, components such as the navigation system, telephone and audio installations work in conjunction with the central display and controls.

The goal here is to standardize operating sequences as much as possible and to concentrate information about the state of systems at a given point in time so as to minimize the possibility of driver error.

Data transfer rate up to 125 kbps. Live broadcast of audio and video data is not possible in this area.

• Diagnostic programs. For diagnostic purposes, the CAN system is used in an already existing network to diagnose the connected ECUs. The current general form of diagnosis using the “K” line (ISO 9141) will not be sufficient in the future.

The data transfer rate is planned to be 500 kbps.

• Application of systems in real time. The use of systems in real time is necessary to control the movement of the car.

Electrical systems such as engine management, shift control and Electronic Stability Program (ESP) work with each other on a network.

Baud rates ranging from 125 kbps to 1 Mbps (high-speed CAN bus) are required in order to guarantee real-time performance.

Rice. 64 Line bus topology diagram. 1 - transmission control unit, 2 - instrument cluster, 3 - engine control unit, 4 - ABS / ESP systems control unit.

ECU operation in the network

The networking strategy provides that electronic systems such as electronic engine control, anti-lock brake system (ABS), traction control (TCS), electronic stability program (ESP), electronic shift control in automatic transmission, etc. are connected one with the other via the CAN interface.

Within a linear bus topology, ECUs are considered equal “partners” (Fig. 64). The advantage of this structure, known as the ‘Multi-Master’ principle, is that the failure of one unit assigned to it does not affect the others. The possibility of a general failure is thus significantly lower than in other logic structures, such as, for example, in closed circuits or hierarchical structures, in which the failure of one system or the central computer causes the failure of the entire structural system.

Typical data rates range from 125 kbps to 1 Mbps. The speeds must be so high in order to guarantee the desired performance in real time. This means, for example, that engine load data from its ECU are fed to the gearbox ECU within a few milliseconds.

Rice. 65 Message addressing and filtering.

Associative Data Addressing

The CAN data system does not address each terminal individually, but instead assigns each “message” a fixed “identifier” of 11 bits (standard format for cars) or 29 bits (long format for commercial vehicles). Thus, the identifier contains the content of the message (for example, the engine speed).

Several signals can be included in one message, such as the number of switching positions.

Each station (ECU) processes only those messages, the identification of which is stored in their own list, which must be received (message filtering, Fig. 65).

All other messages are simply ignored. This operation can be performed by a dedicated CAN module (Full-CAN), so that less load is placed on the microprocessor. The CAN core modules read all messages and then the microprocessor fetches the appropriate memory.

With an associative data addressing system, a single signal can be sent to multiple blocks. This transmitter should simply send its signal directly to the data bus network via the ECU so that the signal is available to all receivers. In addition, since other units may be added to the existing CAN system in the future, a variety of equipment options may be involved. If the ECU requires additional information that the data bus has, then all that is required is simply to call it.

Prioritization

The identifier not only indicates the content of the data, but also determines the priority of the message. Signals subject to rapid changes (eg speed) must obviously be received without delay and without loss of data. As a result, these rapidly changing signals have a higher priority rating than signals whose rate of change is relatively slow (eg, engine coolant temperature). In addition, messages are sorted according to their “importance” (for example, functions relating to work safety are classified as especially “important”). There are never two or more messages of the same priority on a data bus.

Arbitration bus

Each block can start transmitting the highest priority messages as soon as the bus is idle. If several blocks start data transmission at the same time, then the resulting bus access conflict is resolved by granting the first access to the message with the highest priority, without any form of delay and without loss of data bits (indestructible protocol). This is the case when using "recessive" (logical 1) and "dominant" (logical 0) bits - by means of dominant bits, recessive bits are "overwritten". Transmitters with low priority messages automatically become receivers and retry their message as soon as the data bus becomes free again. In order for all messages to be able to enter the bus, the data rate on the bus must match the number of blocks working with this bus. For those signals that are constantly pulsating (for example, the engine speed), the cycle time is determined.

Rice. 66 Message format.

Message Format

For transmission to the bus, a data frame is generated with a maximum length of 130 bits (standard format) or 150 bits (extended format). This allows you to minimize the waiting time for the next - possibly extremely urgent - data transfer. Data frames include seven consecutive zones (fields) (Fig. 66).

“Start of Frame” determines the start of data transfer and synchronizes all systems;

"Field of Arbitration" concatenates a message identifier and an additional control bit. During the transmission of this field, the transmitting device accompanies the transmission of each bit to check that no other higher priority message blocks are currently transmitting. The control bit decides whether to classify a given message as an "information data frame" or as a "remote signal".

"Control field" contains a code indicating the number of bits in the data frame. This allows the signal receiver to determine that all bits of information have been received.

“Data field” has information content between 0 and 8 bits. A message with data length "0" can be used to synchronize distributed processes.

“CRC (Cyclic Redundancy Check) field” contains a control word to determine possible interference in data transmission.

“Confirmation Area” contains an acknowledgment signal, in which all receiving devices indicate the reception of intact signals, regardless of whether they have been processed or not.

"End of frame" indicates the end of receiving the message.

Built-in diagnostics

The CAN data bus system is equipped with a number of monitoring functions to detect errors. These functions include a test signal in the "data frame" as well as a tracking function whereby each transmitter receives its own signal again and can thus detect any deviations from it.

If the system detects an error, it sends a so-called “error flag”, which stops the ongoing data transfer. This prevents other blocks from receiving incorrect data.

In the event of damage to the control unit, it may happen that all transmitted data, including those containing no errors, will be marked with an “error flag”. To prevent this, the CAN system includes a special function that can distinguish between intermittent or permanent errors or interference and therefore localize faults in blocks. This process is based on a statistical analysis of error conditions.

Standardization

The International Organization for Standardization (ISO) and SAE have set standards for the CAN communication system in automotive applications:

• ISO 11519-2 - for low-speed information transfer - speed up to 125 kbps;
• ISO 11898 and SAE J22584 (passenger cars) and SAE J1939 (trucks and buses) - for high-speed information transfer - more than 125 kbps.

ISO standards for CAN diagnostics (ISO 15756 - draft) are in preparation.

A modern car is partly a computer on wheels, or, to be more precise, a computer that controls the movement of the wheels. Most of the mechanical parts of the car have long been superseded, and if they remain, they are completely and completely controlled by the “electronic brain”. Of course, it is much easier to drive a computerized car, and the designers of such cars think about the safety in the first place.

However, no matter how perfect the design of electronic control units (ECUs) is, they can still fail. This situation is not the most pleasant, and due to the complexity of the device, it is not necessary to talk about self-repair (although there are such craftsmen). In today's article, we will talk about what malfunctions can happen to an ECU, how they can be caused, and how to diagnose them correctly.

1. Causes of ECU failure: what should you be prepared for?

First of all, the electronic control unit of a car, or simply, is a very complex and important computer equipment. In the event of a malfunction of this device, incorrect operation of all other automotive systems may occur. In some cases, the car may stop working altogether, including the failure of the transmission, chargers and control sensors.

Electronic units are different and can control different devices. At the same time, all systems still actively interact with each other and transmit important information for adjusting all functions. The most basic of them is the car engine ECU. Despite its structural simplicity, it performs a lot of complex tasks:

1. Control of fuel injection into the combustion chamber of a car.

2. Throttle valve adjustment (both while driving and while the engine is idling).

3. Management of the ignition system.

4. Exhaust gas composition control.

5. Valve timing control.

6. Coolant temperature control.

If we talk specifically about the engine ECU, then all the data received by it can also be taken into account when the anti-lock brake system is working, and when the passive safety system is working, and in the anti-theft system.

The reasons for the failure of the ECU can be very diverse. In any case, this does not bode well for the car owner, since this device cannot be repaired. Even at service stations, they simply change it to a new one. But be that as it may, it is necessary to understand in great detail what can cause a breakdown. With this knowledge, you will be able to ensure the maximum possible protection of the device from such troubles in the future.

According to auto electricians, most often the computer fails due to overvoltage in the electrical network of the car. The latter, in turn, may occur due to a short circuit in one of the solenoids. However, this is not the only possible reason:

1. Damage to the device can occur due to any mechanical impact. This can be an accidental impact or very strong vibrations that can cause microcracks in the computer boards and the soldering points of the main contacts.

2. Overheating of the unit, which most often occurs due to a sharp temperature drop. For example, when you are trying to start the car at high speeds in severe frost, squeezing the maximum out of the capabilities of the car and all its systems.

3. Corrosion, which can occur due to changes in air humidity, as well as due to water ingress into the engine compartment of the car.

4. Moisture ingress directly into the control unit itself due to depressurization of the device.

5. The intervention of outsiders in the device of electronic systems, as a result of which a violation of their integrity could occur.

If you wanted to “light up” the car without first turning off the engine.

If the terminals were removed from the car battery without first turning off the engine.

If the terminals were reversed when connecting the battery.

If the starter was turned on, but no power bus was connected to it.

However, whatever may have caused the malfunction of the computer, any repair work can only be carried out after a full professional diagnosis has been carried out. On the whole, The nature of the device malfunction will tell you about malfunctions in other systems. After all, if they are also not eliminated, then the new control unit will burn out in the same way as the old one. That is why in the event of a computer burnout, it is very important to establish the true cause of the breakdown and immediately eliminate it.

But how to determine that the control unit really failed, and not some other system? This can be understood by a number of the very first signs that may appear in such a situation:

1. The presence of obvious physical damage. For example, burnt contacts or conductors.

2. Inoperative signals for controlling the ignition system or fuel pump, idle mechanism and other mechanisms that are under the control of the unit.

3. Lack of indicators from different sensors of control systems.

4. Lack of communication with the diagnostic device.

2. How to check the computer: practical advice for motorists who do not want to go to the service station.

Fortunately, even if you have neither the money nor the desire to go to the service station, and the ECU does not want to give any signs of life, there is a sure way to determine what is the cause of the breakdown. Perhaps this is due to the presence of a built-in self-diagnosis system on each vehicle control unit. It allows you to determine the possible cause of a breakdown without the use of special diagnostic equipment.

But let's make a small digression and talk about some features of the car engine control unit. This electronic device is a mini-computer capable of performing tasks assigned to it in real time. At the same time, all specialized tasks can be divided into three categories:

1. Processing and analysis of signals that come to the unit from all sensors.

2. Calculation of the necessary impact, which is necessary to control all vehicle systems.

3. Control over the operation of actuators, that is, those that receive a signal from the control unit.

However, in order to be able to check the status of the engine control unit, first of all, it is necessary to perform a series of manipulations in order to connect to it. To do this, you will need either a special tester, which, for obvious reasons, not everyone has, or a laptop with a special program pre-installed on it. What kind of program should this be? It is designed to read diagnostic data from the control unit. You can install it either from the Internet or from a disk purchased at the car market.

However, it is worth considering that different models of control units can be installed on different car models. Based on this, it is necessary to select a diagnostic program for a laptop and, of course, the method of verification itself. We will tell you how to diagnose the model ECU Bosch M7.9.7. This ECU model is quite common both on VAZ cars and on foreign cars.

As for the program for diagnostics, in this case we will use KWP-D. We note right away that, in addition to the program itself for performing diagnostics, you will definitely need a special adapter that can support the KWP2000 protocol. With its connection, the diagnostic process itself begins:

1. We insert one end of the adapter into the port of the electronic control unit, and the other end into the USB port of your laptop.

2. We turn the key in the car ignition and run the diagnostic program on the laptop.

3. Immediately after starting, a message should appear on the laptop display confirming the successful start of the error check in the operation of the electronic control unit.

5. Pay attention to the section called DTC, since it is in it that all the malfunctions that the engine will issue will be displayed. Errors will appear in the form of special codes, which can be decrypted by going to a special section, which is called “Codes”.

6. If not a single error has appeared in the DTC section, then you can rejoice - the car engine is in perfect condition.

However, it is also not worth ignoring the other sections of the table, since they can also contain very important information that can explain computer malfunctions. Among them:

Section UACC- it displays all the data characterizing the state of the car battery. If everything is in order with this device, then its indicators should be in the region from 14 to 14.5 V. If the indicator obtained as a result of the test is below the specified value, you should carefully check all electrical circuits that depart from the battery.

THR Section- Throttle position parameters will be displayed here. If the vehicle is idling and there is no problem with this item, this section will display a value of 0%. If it is higher, seek help from a specialist.

Section QT is fuel consumption control. Since the car is idling, an indicator should appear in the table that is in the range from 0.6 to 0.0 liters per hour.

LUMS_W section- the state of the crankshaft during rotations. During normal operation, its rate should not exceed 4 revolutions per second. If the number of revolutions is higher, then uneven ignition occurs in the engine cylinders. In addition, the problem may be hiding in high-voltage wires or candles.

3. What is needed to check the ECU, or how do professionals cope with this task?

Without special equipment, it is simply impossible to carry out a full check of the car's engine control unit. But thanks to its presence, the diagnostic process becomes a very simple task. The only problem is to purchase this special equipment, which, in fact, will do all the work for you.

So, what may a driver need to diagnose an electronic control unit? First of all, this oscilloscope. With it, you can get data on the operation of absolutely all vehicle systems. In this case, all received data will be displayed either in graphical or numerical form.

After taking the figures obtained from your car, you will need to compare them with standard indicators. Based on this, you will be able to determine in which system there is a malfunction, and you can fix it. The only disadvantage of the oscilloscope is its cost, which not everyone can afford.

But in addition to the oscilloscope, you can use a special tool to diagnose the state of the control unit. motor tester. Its main function is to determine the indicators that come from all the electronic systems of an automobile engine. For example, it allows you to determine the drop in speed when the cylinders are turned off, as well as the presence of vacuum in the intake manifold. But it costs no less than an oscilloscope.

Since the computer does not fail so often, and it is still better to entrust the troubleshooting of this unit to specialists, the purchase of such expensive devices is not always a rational decision. Moreover, you yourself will not always be able to correctly read the information from their display. Therefore, if any signs of a malfunction of the computer appear, we recommend that you seek help from specialists. After all, with your manipulations, you can do more harm than good to your car.

Every modern vehicle is equipped with an electronic engine management system (ECM). The main element of the system is the engine control unit, which ensures optimal operation of the power unit. What kind of device is this, what functions does the computer perform, what is its principle of operation? You can find answers to these and other questions regarding the ECM below.

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ECU description

To begin with, consider the description of the car engine ECU, its typical parameters, and also tell you where the device is located. Let's start with the main options assigned to this device.

Functional

So what is an ECU in a car? The engine control unit is a device used to receive signals from controllers and sensors, as well as their subsequent processing and transmission of commands to actuators. The data received by the motor control system in the car is processed according to the algorithm established by the manufacturer. After processing the information, the electronic engine control unit transmits the appropriate commands to the actuators and components.

The electronic engine control system makes it possible to optimize important parameters for the operation of the power unit, in particular:

• to establish the most optimal fuel consumption;
• control the composition and ratio of harmful substances in exhaust gases;
• to control the torque indicators;
• ensure the most optimal power of the power unit;
• adjust the position of the throttle valve;
• control the operation of the ignition system;
• adjust the operation of the exhaust gas recirculation system;
• to control the phases of the gas distribution mechanism;
• adjust the antifreeze temperature if necessary.

It should be borne in mind that these are far from all the functions that an electronic engine control unit can perform. These are the most basic parameters, but depending on the ECM model, the control model may perform other options. This device also makes it possible to diagnose the car as a whole, if malfunctions were recorded in the operation of certain nodes. The need for a check may be indicated by the appearance of the Check light on the instrument panel.

The control lamp of the engine management system, which is on the tidy, appears if the ECM has detected malfunctions in the functioning of certain components. To obtain more accurate data on breakdowns, the car owner must carry out computer diagnostics of the system and decipher the resulting combinations of errors (the author of the video is Pavel Ksenon).

Now consider the location of the control module in the car. In most cases, as you can see from the photo, the device is in the car, behind the center console, in the middle. To gain access to the device, it will be necessary to disassemble part of the torpedo. Also, the computer can be located behind the glove box or dashboard, but if it was installed independently, then the installation location is determined by the installer. In some car models, the device is located in the engine compartment.

Components

The two main components of any electronic engine management system are software as well as hardware.

The software, in turn, includes the following computing modules:

1. A control module originally designed to check the vehicle and inspect outgoing signals. Thanks to this module, if necessary, the impulses are corrected. In addition, the control module even allows you to turn off the engine if necessary (for example, in case of overheating or other problems).
2. An equally important module is functional. It is used to receive signals transmitted to the vehicle control unit from controllers and sensors. When the module receives a signal, it processes it, and then generates certain commands, which are subsequently sent to the actuators (video by Pavel Ksenon).

The ECU circuit also includes hardware, which includes various electronic elements - microcircuits, a processor, etc. The design of the control module has a special analog-to-digital converter designed to capture analog signals transmitted by controllers and sensors. With the help of a converting device, the received pulses are converted into a digital format, with which the processor itself subsequently works. Also, this element converts pulses in reverse order, if there is a need to transmit a signal from the microprocessor.

Separately, it should be said about the protection of the module. In the event of a car break-in, an attacker can easily gain access to the computer by opening the torpedo. ECU protection can be provided by installing an additional safe or a special tank that will prevent a criminal from gaining access to the device. Here it is necessary to note such a moment as the interchangeability of the ECU.

The interchangeability of the car's ECU allows you to replace the control module in the car in the event of its failure, however, this will also allow the criminal to change the unit installed in the car to his own. Thanks to this, an attacker will be able to bypass the anti-theft system, which is why it is important to take care of protecting the module.

Principle of operation

If we talk about the principle of operation, then the engine control unit receives signals from various sensors, their number may vary depending on the type of car:

• air flow signals from the DMRV;
• about the temperature of the engine;
• about the position of the crankshaft, as well as the frequency of its operation:
• about rough road;
• about the speed of the car, etc.

Processing the received signals, the control unit transmits commands to various systems:

1. Machine ignition. As you know, a vehicle, depending on which engine is installed on it, can be equipped with one or more coils. In accordance with the received signal, the ignition system determines the optimal mode for supplying a spark, which is necessary to ignite the air-fuel mixture.
2. On the dashboard. The check lamp, as mentioned above, is the link between the unit and the driver. Its appearance on the tidy may be due to the detection of ECM malfunctions in the operation of certain nodes. In some cases, error messages indicate a malfunction of certain sensors.
3. On the injectors of the power unit, with the help of which the most optimal injection of the air-fuel mixture into the internal combustion engine cylinders is carried out. It should be borne in mind that the frequency of change in the volume of the mixture can be different.
4. On devices for testing the ECM (the author of the video is Pavel Ksenon).

Pros and cons of an electronic engine control unit

Let's look at the benefits first:

• with the help of the ECM, the main operating parameters of the vehicle are optimized;
• reduced air flow;
• a more simplified start of the power unit is provided;
• the car owner no longer needs to adjust the parameters of the motor, almost everything that is needed is automatically adjusted;
• if the engine is working correctly, then the correct operation of the computer will achieve optimal parameters in terms of environmental cleanliness.

Main disadvantages:

1. The cost of the ECU is quite high. If the device fails, you can try to repair it, but if this does not help, then the device must be replaced.
2. In order for the system to work correctly, the vehicle wiring must be intact, in particular, we are talking about the section of the power supply circuit of the ECM itself.
3. For optimal performance, the driver must refuel only high-quality fuel.
Photo 3. Scheme of interaction between the computer and automotive systems