EURO-5 Engine Management System Niva Chevrolet
The electronic engine management system (ECM) consists of a controller, engine and vehicle operating parameter sensors, and actuators
Controller
The controller is a special-purpose mini-computer, it includes a random access memory (RAM), a programmable read-only memory (EPROM) and an electrically reprogrammable memory (ERPROM).
The RAM is used by the microprocessor for temporary storage of current information about engine operation (measured parameters) and calculated data.
Also, codes of emerging faults are recorded in the RAM. This memory is volatile, i.e. when the power supply is interrupted (the battery is disconnected or the wiring harness is disconnected from the controller), its contents are erased.
The EPROM stores the engine control program, which contains a sequence of operating commands (algorithms) and calibration data (settings).
The EPROM determines the most important engine operating parameters: the nature of changes in torque and power, fuel consumption, ignition timing, exhaust gas composition, etc. The EPROM is non-volatile, i.e. the contents of its memory do not change when the power supply is disconnected.
The EPROM stores the identifiers of the controller, engine and vehicle.
Records operating parameters, as well as violations of engine and vehicle operating modes. It is a non-volatile memory.
The controller is the central device of the engine management system.
It receives information from sensors and controls actuators, ensuring optimal engine operation at a given level of vehicle performance.
The controller is located in the passenger footwell and is attached to the front panel.
The controller controls actuators such as fuel injectors, an electric throttle body, an ignition coil, an oxygen sensor heater, an adsorber purge valve, and various relays.
The controller controls the switching on and off of the main relay (ignition relay), through which the supply voltage from the battery is supplied to the system components (except for the electric fuel pump, electric fan, control unit, and APS status indicator).
The controller switches on the main relay when the ignition is switched on.
When the ignition is switched off, the controller delays the switching off of the main relay for the time required to prepare for the next switching on (completion of calculations, setting the throttle valve to the position preceding the start engine).
When the ignition is turned on, the controller, in addition to performing the above functions, exchanges information with the APS (if the immobilization function is enabled).
If the exchange determines that access to the car is allowed, the controller continues to perform engine control functions. Otherwise, the engine is blocked.
The controller also performs the system diagnostic function. It determines the presence of faults in the system elements, turns on the alarm and saves stores codes in its memory that indicate the nature of the malfunction and help the mechanic carry out repairs.
Mass Air Flow Sensor
The engine management system uses a hot-wire MAF with a digital output signal frequency response. It is located between the air filter and the intake pipe hose.
The MAF signal is a frequency (Hz) signal, the pulse repetition rate of which depends on the amount of air passing through the sensor (increases with increasing air flow).
The diagnostic tool reads the sensor readings as air flow in kilograms per hour.
If a malfunction occurs in the MAF circuit, the controller stores its code in its memory and turns on the alarm. In this case, the controller replaces the sensor readings with a fixed air temperature value (20 °C).
Throttle position sensors (TPS)
Two TPSs are used in the system with EPS. TPS are part of the throttle pipe with an electric drive.
TPS is a potentiometric resistor, to one of the terminals of which the reference voltage (5 V) from the controller is supplied, and to the second "ground" from the controller.
The output signal of TPS is supplied to the controller from the terminal connected to the movable contact of the potentiometer.
The controller controls the position of the throttle valve using an electric drive in accordance with the position of the accelerator pedal.
Based on the TPS readings, the controller monitors the position of the throttle valve.
When the ignition is turned on, the controller sets the valve to the pre-start position, the degree of opening of which depends on the temperature of the coolant.
In the pre-start position of the throttle valve, the output signal of TPS 1 should be within 0.65-0.79 volts, the output signal of TPS 2 is within 4.21-4.35 V.
If the engine is not started and the accelerator pedal is not pressed within 15 seconds, the controller de-energizes the throttle valve electric drive and the throttle valve is set to 7-8% throttle opening.
In the de-energized state (LIMP HOME) of the throttle valve electric drive, the output signal of TPS 1 is within 0.80-0.85 volts, the output signal of TPS 2 is within 4.15-4.20 V.
Then, if no action is taken within 15 seconds, the throttle valve 0-position test ("training") mode will begin - complete closing and opening of the throttle valve to the pre-start position and then the throttle valve electric drive will again switch in de-energized mode.
At any position of the throttle valve, the sum of the signals from TPS 1 and TPS 2 must be equal to (5±0.1) V.
If a malfunction of the TPS circuits occurs, the controller de-energizes the throttle valve electric drive, stores its code in its memory and turns on the alarm. In this case, the throttle valve is set to a position of 7-8% throttle opening.
Electronic accelerator pedal (EPA)
Cars with an electronic throttle unit use an electronic accelerator pedal, which electrically transmits a signal about the position of the accelerator pedal to the controller.
The electronic gas pedal is located on the bracket under the driver's right foot.
The electronic gas pedal uses two accelerator pedal position sensors (APPS).
APPS are potentiometric resistors that are powered by a 5 V controller.
APPS are mechanically connected to the drive from the pedal lever. Two independent springs between the pedal lever and the body create a return force.
Receiving an analog electrical signal from the EPA, the controller generates a signal to control the position of the throttle valve.
The output voltage of the EPA changes proportionally to pressing the accelerator pedal.
When the accelerator pedal is released, the signal of EPA 1 should be within 0.46-0.76 V, the signal of EPA 2 should be within 0.23 ... 0.38 V.
When the accelerator pedal is fully pressed, the signal of EPA 1 should be within 2.80-3.10 V, DPPA 2 signal within 1.40-1.55 V.
At any position of the accelerator pedal, the DPPA 1 signal should be twice as large as the DPPA 2 signal.
Coolant Temperature Sensor (CTS)
The sensor is installed in the engine coolant flow, on the branch pipe that discharges the engine water jacket.
The sensitive element of the coolant temperature sensor is thermistor, i.e. a resistor whose electrical resistance changes depending on temperature.
High temperature causes low resistance, and low coolant temperature causes high resistance.
The controller outputs 5 V to the coolant temperature sensor circuit.
Knock sensor (KS)
installed on the cylinder block.
The piezoelectric sensitive element of the DD generates an AC voltage signal, the amplitude and frequency of which correspond to the parameters of engine vibrations.
When detonation occurs, the amplitude of vibrations of a certain frequency increases. The controller adjusts the ignition timing to suppress detonation.
Oxygen Sensor Control (UDC)
The most effective reduction in the toxicity of exhaust gases from gasoline engines is achieved with a mass ratio of air and fuel in the mixture (14.5-14.6): 1.
This ratio is called stoichiometric.
With this composition of the fuel-air mixture, the catalytic converter most effectively reduces the amount of hydrocarbons, carbon monoxide and nitrogen oxides emitted from the exhaust gases.
To optimize the composition of exhaust gases in order to achieve the greatest efficiency of the neutralizer, closed-loop fuel supply control with feedback on the presence of oxygen in the exhaust gases is used.
The controller calculates the injection pulse duration based on parameters such as air mass flow, crankshaft speed, coolant temperature, etc.
To adjust the injection pulse duration calculations, information on the presence of oxygen in the exhaust gases, which is provided by the oxygen sensor, is used.
The UDC is installed on the exhaust pipe. Its sensitive element is located in the exhaust gas flow. The UDC generates a voltage that varies in the range of 50-900 mV.
This output voltage depends on the presence or absence of oxygen in the exhaust gases and on the temperature of the UDC sensing element.
When the UDC is cold, there is no output signal from the sensor, since in this state its internal electrical resistance is very high - several megohms.
As the sensor warms up, the resistance drops and the ability to generate an output signal appears.
For efficient operation, the UDC must have a temperature of at least 300 ° C.
For rapid warming up after starting the engine, the UDC is equipped with an internal electric heating element controlled by the controller.
The duty cycle of the heater control pulse signals (the ratio of the duration of the on state to the pulse repetition period) depends on the UDC temperature and the engine operating mode.
If the sensor temperature is above 300 ° C, then at the moment of transition through the stoichiometry point, the output signal of the sensor switches between a low level (50-200 mV) and a high level (700...900 mV).
A low signal level corresponds to a lean mixture (the presence of oxygen), a high signal - to a rich mixture (no oxygen).
Description of the circuit
The controller supplies a stable reference voltage of 1.6 V to the UDC circuit. When the UDC is not warmed up, the output voltage of the sensor is in the range of 1.2-1.6 V.
As the sensor warms up, its internal resistance decreases, and it begins to generate a changing voltage that goes beyond this range.
Based on the change in voltage, the controller determines that the UDC has warmed up, and its output signal can be used to control closed loop fuel injection control.
During normal closed loop fuel injection system operation, the O2S output voltage alternates between low and high levels.
O2 Sensor Poisoning
The O2S can be poisoned by using leaded gasoline or by using room temperature vulcanizing sealants containing high amounts of highly volatile silicone (silicon compounds) during assembly.
Silicone vapors can enter the crankcase ventilation system and be present during combustion. The presence of lead or silicon compounds in the exhaust gases can cause the O2 sensor to fail.
O2 sensor circuit faults, sensor defects, sensor poisoning, or unheated condition can cause the signal voltage to remain in the range of 1.2-1.6 V for a long time. In this case, the controller will store a corresponding fault code.
Fuel supply will be controlled in an open circuit.
If the controller receives a signal with a voltage indicating a long-term lean condition, the corresponding fault code (low oxygen sensor signal) will be stored in its memory.
The cause of the fault may be a short circuit in the O2 sensor output circuit to ground, a leak in the air intake system, or low fuel pressure.
If the controller receives a signal with a voltage indicating a long-term rich condition, the corresponding fault code (high oxygen sensor signal) will be stored in its memory. oxygen).
The cause of the malfunction may be a short circuit of the output circuit of the oxygen sensor to a voltage source or increased fuel pressure in the injector rail.
When oxygen sensor malfunction codes occur, the controller controls the fuel supply in open loop mode.
Oxygen sensor maintenance
If the harness, connector or plugs of the oxygen sensor are damaged, the oxygen sensor must be replaced. Repair of the harness, connector or plugs is not allowed.
For normal operation, the oxygen sensor must communicate with atmospheric air. Communication with the atmospheric air is ensured by air gaps in the sensor wires.
Attempts to repair wires, pads or plugs may result in a disruption of communication with the atmospheric air and deterioration of the DK operation.
When servicing the DK, the following requirements must be observed:
Do not allow contact cleaning fluid or other materials to come into contact with the sensor or harness pads.
These materials may get into the DK and cause malfunction. In addition, do not damage the wire insulation, leading to their exposure.
Do not strongly bend or twist the DK harness and the injection system wiring harness connected to it. This may disrupt the flow of atmospheric air into the DK.
To prevent malfunction due to water ingress, it is necessary to prevent damage to the seal on the periphery of the control system harness block.
Diagnostic oxygen sensor (DKS)
A catalytic converter is used to reduce the content of hydrocarbons, carbon monoxide and nitrogen oxides in the exhaust gases.
The converter oxidizes hydrocarbons and carbon monoxide, causing them to are converted into water vapor and carbon dioxide. The neutralizer also restores nitrogen from nitrogen oxides.
The controller monitors the oxidation-reduction properties of the neutralizer by analyzing the signal from the diagnostic oxygen sensor installed after the neutralizer.
The DDC operates on the same principle as the UDC. The ODS generates a signal indicating the presence of oxygen in the exhaust gases at the inlet to the neutralizer.
The signal generated by the ODS indicates the presence of oxygen in the exhaust gases after the neutralizer.
If the neutralizer is operating normally, the ODS readings will differ significantly from the ODS readings.
The output signal of a warmed-up diagnostic oxygen sensor when operating in feedback mode, with a serviceable neutralizer in steady-state mode, should be in the range from 590 to 750 mV and should not repeat the ODS signal.
If a malfunction occurs in the circuits or the diagnostic oxygen sensor itself, the controller stores its code in its memory and turns on the alarm, signaling the presence of a malfunction.
Maintenance requirements ation and the procedure for replacing the DDC do not differ from those described above for the UDC.
Vehicle speed sensor
produces a pulse signal that informs the controller about the speed of the vehicle.
The DSA is installed on the input shaft of the transfer case.
When the drive wheels rotate, the DSA generates 6 pulses per meter of vehicle movement. The controller determines the vehicle speed based on the pulse repetition rate.
If the DSA circuits are faulty, the controller stores its code in its memory and turns on the indicator.
Crankshaft position sensor
Mounted on the camshaft drive cover at a distance of about 1±0.4 mm from the top of the tooth of the timing disk, fixed on the engine crankshaft.
The timing disk is combined with the generator drive pulley and is a gear wheel with 58 teeth located at 6° pitch and a "long" depression for synchronization formed by two missing teeth.
When the middle of the first tooth of the toothed sector of the disk after the "long" depression is aligned with the crankshaft position sensor axis, the engine crankshaft is in the position of 114° (19 teeth) before the top dead center of the 1st and 4th cylinders.
When As the setting disk rotates, the magnetic flux in the sensor's magnetic circuit changes, inducing AC voltage pulses in its winding.
The controller determines the position and rotation speed of the crankshaft based on the number and frequency of these pulses and calculates the phase and duration of the injector and ignition coil control pulses.
The crankshaft position sensor wires are protected from interference by a screen shorted to ground.
If a malfunction occurs in the crankshaft position sensor circuit, the engine stops running, the controller stores the malfunction code in its memory and turns on the alarm.
Phase sensor
is installed on the cylinder head boss.
The sensor operates on the Hall effect.
There is a special pin on the engine camshaft.
When the pin passes opposite the end of the sensor, the sensor sends a low-level voltage pulse (about 0 V) to the controller, which corresponds to the position of the piston of the 1st cylinder in the stroke compression.
The phase sensor signal is used by the controller to organize sequential fuel injection in accordance with the order of operation of the engine cylinders.
If a malfunction of the circuits or the phase sensor itself occurs, the controller stores its code in its memory and turns on the indicator.
Brake signal switch
The switch is part of the brake pedal assembly and is designed to send the corresponding signals to the ECM controller about the driver pressing / releasing the brake pedal.
In control systems In the case of E-throttle by wire (E-throttle) the signals from the brake pedal switch play an important role, as they are used by the safety function of the ECM software.
For this reason, it is very important to ensure that the brake light switch is always in working order.
If its functional switching characteristic does not correspond, for example, if the adjustment values indicated in the instructions change spontaneously (due to vibrations of the pedals), the brake pedal switch signals play an important role, since they are used by the ECM software.
For this reason, it is very important to ensure that the brake light switch is always in working order.
If its functional switching characteristic does not correspond to the instructions, for example, if the adjustment values indicated in the instructions change spontaneously (due to vibrations of the pedals, and brakes, wear of the switch and pedal unit), the car engine can go into emergency mode with forcibly reduced power.
The value of the adjustment gap of the switch should be within 0.4±0.1 mm (Fig. 22).
The brake light switch has two groups of contacts.
The first group of contacts switches the voltage from terminal "15" of the ignition switch, the second - the voltage from terminal "30" of the ignition switch, which is supplied to the brake light lamp. Both of these signals are sent to the ECM.
When the brake pedal is released, the contacts of the first group should be normally closed, and the contacts of the second should be normally open.
If the brake light switch is faulty, the controller stores its code in its memory and turns on the indicator.
The fault code is also stored if the gap (0.4 ± 0.1 mm) between the head of the movable rod 3 and the housing of the switch 1 is incorrectly adjusted.
Clutch pedal position signal switch
The switch is part of the clutch pedal assembly and is designed to send a signal to the ECM about the pressed clutch pedal.
The switch has one group of contacts that switches voltage from terminal "15" of the ignition switch.
When the clutch pedal is pressed, the contacts are open.
The signal from the clutch pedal position switch is used by the ECM software to improve the driving characteristics of the car.
If the VSPPS malfunctions, the controller stores its code in its memory and turns on the indicator.
The value of the adjustment gap should be within 0.3±0.1 mm (Figure 24).
