10.7.1. Features of a design
The engine installed on the Chevrolet Lanos cars is equipped with an electronic control system of the engine with the distributed fuel injection. This system provides performance of modern norms on toxicity of emissions and to evaporations at preservation of high road performance and low fuel consumption.
The actuation device in system is the electronic control unit (ECU). On the basis of information obtained from sensors, EBU counts parameters of regulation of injection of fuel and management of an ignition advancing corner. Besides, according to the put algorithm of EBU operates operation of the electric motor of the fan of the cooling system of the engine and electromagnetic coupling of turning on of the compressor of the conditioner, performs function of self-diagnostics of elements of system and notifies the driver on the arisen malfunctions.
At failure of separate sensors and EBU executive mechanisms includes the emergency operation providing operability of the engine.
The amount of the fuel given by nozzles is defined by duration of an electric signal from EBU. The electronic block traces data on a condition of the engine, counts the need for fuel and determines the necessary duration of supply of fuel by nozzles (signal duration). For increase in amount of the given fuel duration of a signal increases, and for fuel supply reduction — decreases.
The control system of the engine along with an electronic control unit includes sensors, actuation mechanisms, sockets and safety locks.
The Electronic Control Unit (ECU) is connected by electric wires with all sensors of system. Obtaining from them information, the block carries out calculations according to the parameters and a control algorithm which are stored in memory of the programmable read-only memory (PROM) and operates actuation mechanisms of system. The version of the program which is written down in memory of PPZU is designated by number assigned to this modification of EBU.
The control unit finds malfunction, identifies and remembers its code even if the refusal is unstable and disappears (for example, because of bad contact). The alarm lamp of malfunction of a control system of the engine in a combination of devices dies away through 10 from later maintenance of the refused knot.
After repair the code of malfunction which is stored in memory of the control unit needs to be erased. For this purpose power off the block on 10 with (take out a safety lock of a power-supply circuit of an electronic control unit or disconnect a wire from the minus plug of the rechargeable battery).
The block feeds with a direct current of 5 and 12 V various sensors and switches of a control system. As the electric resistance of power-supply circuits high, the control lamp connected to system conclusions does not light up. On conclusions of EBU it is necessary to use the voltmeter to determination of supply voltage with an internal resistance not less than 10 megohms.
EBU is not suitable for repair, in case of refusal it needs to be replaced.
The diagnostic socket serves for a conclusion from memory of EBU of codes of the malfunctions revealed during the work of a control system of the engine. Designation and an arrangement of conclusions in the diagnostic socket is shown in fig. 10.6.
Purpose of conclusions:
And – "weight";
B — a diagnostic conclusion;
Е — a conclusion "plus".
Fig. 10.6. Diagnostic socket
The diagnostic socket is located in interior of the car in a niche for the driver's legs on the right side under the dashboard. The mode of self-diagnostics joins at connection of a conclusion "In" (a diagnostic conclusion) with a conclusion "And", connected to "weight", and inclusion of ignition (the engine should not work). It is possible to connect the scanner which reads out information from the consecutive line of data to the diagnostic socket.
The sensor of temperature of cooling liquid is installed in the engine cooling system. A sensitive element of the sensor is the thermistor which electric resistance changes in inverse proportion to temperature. At a low temperature of cooling liquid (–40 °C) resistance of a thermistor makes about 100 kOhm, at temperature increase to +130 °C — decreases to 70 Ohms.
The electronic block feeds temperature sensor chain with constant basic tension. Sensor signal tension as much as possible on the cold engine also decreases in process of its warming up. The electronic block determines temperature of the engine by value of tension and considers it when calculating adjusting parameters of injection and ignition. At failure of the sensor or violations in a chain of its connection of EBU establishes a code of malfunction and remembers it. For elimination of malfunction check reliability of contact connections in conducting to the sensor or replace the sensor.
The air temperature sensor on an admission (it is pasted in the airbringing sleeve) is similar on a design to the sensor of temperature of cooling liquid, in it the thermistor changing the resistance depending on temperature is also used.
Resistance of a thermistor makes 100 kOhm at a temperature of -40 °C, and at temperature increase to +130 °C decreases to 70 Ohms.
EBU feeds a sensor chain with constant basic tension. Sensor signal tension as much as possible when air in an inlet pipe cold, also decreases in process of increase in its temperature. Determines air temperature on an admission by value of tension of EBU and introduces amendments when calculating a corner of an advancing of ignition. At failure of the sensor or violations in a chain of its connection of EBU establishes a code of malfunction and remembers it. If EBU continues to give a malfunction code at correct contact connections in conducting, replace the air temperature sensor.
The sensor of provision of a bent shaft of inductive type is intended for synchronization of work of an electronic control unit with VMT of pistons of the 1st and 4th cylinders and the angular provision of a bent shaft.
The sensor is installed in a forward part of the engine opposite to the setting disk on a pulley of a bent shaft. The setting disk represents a cogwheel with equidistant hollows. Two teeth are cut off for creation of an impulse of synchronization (a "basic" impulse) which is necessary for coordination of operation of the control unit with VMT of pistons in the 1st and 4th cylinders.
At rotation of a bent shaft teeths change magnetic field of the sensor, directing impulses of tension of alternating current. The control unit determines the frequency of rotation of a bent shaft by signals of the sensor and gives impulses on nozzles.
At failure of the sensor launch of the engine is impossible.
The sensor of provision of a butterfly valve is installed sideways on throttle knot and connected with an axis of a butterfly valve.
The sensor represents a potentiometer on which one end moves "plus" supply voltages (5 V), and other end is connected to "weight".
From the third conclusion of a potentiometer (from the toddler) there is an output signal to an electronic control unit.
When the butterfly valve turns (from impact on a pedal of management), tension at the sensor exit changes. At the closed butterfly valve it is lower than 0,5 Century. When the gate opens, tension at the exit of the sensor grows, at completely open gate it has to be more than 4 Century.
Tracing the output tension of the sensor, the controller corrects supply of fuel depending on the angle of opening of a butterfly valve (i.e. at the request of the driver).
The sensor of provision of a butterfly valve does not demand adjustment as the control unit perceives idling (i.e. full closing of a butterfly valve) as a zero mark.
The sensor of absolute pressure in an inlet pipe will transform depression in this pipe to the voltage by which value the electronic control unit determines engine loading. The sensor is installed in a motor compartment, fixed on a partition of a board of a front and connected to an inlet pipe a rubber tube. The output tension of the sensor changes according to pressure in an inlet pipe — from 4,9 B (at completely open gate) to 0,3 B (at the closed gate). At the idle engine the control unit determines atmospheric pressure by tension of the sensor and adapts parameters of regulation of injection to concrete height above sea level. The values of atmospheric pressure which are kept in memory are periodically updated at uniform motion of the car and during full opening of a butterfly valve.
The sensor of speed of the car is installed on the transmission. The principle of operation of the sensor is based on Hall's effect. The sensor gives on an electronic control unit rectangular impulses of tension with a frequency proportional to the speed of rotation of driving wheels.
The sensor of concentration of oxygen (lambda probe) will be screwed in a carving opening of a final collector. In a metal flask of the sensor the galvanic cell washed by a stream of the fulfilled gases is located. Depending on the content of oxygen in the fulfilled gases as a result of combustion of fuel-air mix sensor signal tension changes.
Information from the sensor comes to the control unit in the form of signals low (from 0,1 B) and high (to 0,9 B) level. At a signal of low level the control unit obtains information on the high content of oxygen and, therefore, about mix impoverishment. The signal of high level testifies to the low content of oxygen in the fulfilled gases and, therefore, to mix reenrichment.
Constantly tracing sensor signal tension, the control unit corrects amount of the fuel injected by nozzles. At low level of a sensor signal (poor fuel-air mix) the quantity given fuels increases, at the high level of a signal (rich mix) – decreases.
1. Before removing any knots of a control system of fuel injection, disconnect a wire from the minus plug of the rechargeable battery.
2. Do not launch the engine if tips of wires on the rechargeable battery are badly tightened.
3. Never disconnect the rechargeable battery from onboard network of the car at the working engine.
4. At charging of the rechargeable battery disconnect it from onboard network of the car.
5. Do not subject EBU to temperature over 65 ° C in working order and higher than 80 ° C in non-working (for example, in the drying camera). It is necessary to remove EBU from the car if this temperature is exceeded.
6. Do not disconnect from EBU and do not attach to it a wire at the included ignition.
7. Before carrying out electrowelding works on the car disconnect wires from the rechargeable battery and a block of a plait of wires from EBU.
8. Carry out all voltage measurements the digital voltmeter with an internal resistance not less than 10 megohms.
9. The electronic knots applied in system of injection of fuel are calculated on very small tension therefore can be easily damaged by the electrostatic category. Not to allow damage of EBU, do not touch with hands its conclusions.
10. Diagnostics of a control system of the engine in all cases requires the special scanner therefore at emergence of malfunctions of system address on specialized service.