The VAZ-2123 vehicle has been equipped since 2015 with an electronic engine management system with a ME17.9.71 2123-1411020-50 controller to EURO-5 toxicity standards.
The engine electronic management system (EEMS) consists of the controller, sensors of the engine and vehicle operating parameters, as well as actuating devices.
The controller is a special-purpose mini-computer; its composition includes random-access memory (RAM), programmable read-only memory (PROM) and electrically erasable programmable read-only memory (EEPROM).
The RAM is used by the microprocessor for temporary storage of current information about engine operation (measured parameters) and calculation data.
The codes of occurring faults are also recorded in the RAM.
This memory is volatile, i.e. when the electrical supply ceases (disconnection of the battery or disconnection of the wiring harness connector from the controller), its contents are erased.
The PROM stores the engine management program, which contains the sequence of operating commands (algorithms) and calibration data (settings).
The PROM determines the most important parameters of engine operation: the nature of the change in torque and power, fuel consumption, ignition advance angle, exhaust gas composition, etc. The PROM is non-volatile, i.e. the contents of its memory do not change when the power is switched off.
The EEPROM stores the identifiers of the controller, the engine and the vehicle.
It records the operating parameters, as well as violations of the 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 the sensors and controls the actuators, ensuring optimum engine operation at a given level of vehicle performance.
The controller is located in the passenger footwell and is secured to the front panel.
The controller controls the actuators, such as the fuel injectors, the electrically driven throttle body, the ignition coil, the oxygen sensor heater, the canister 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 elements (except the electric fuel pump, the electric fan, the control unit and the 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 necessary to prepare for the next switch-on (completion of calculations, setting of the throttle valve to the position preceding engine start).
When the ignition is switched on, the controller, in addition to performing the functions mentioned above, exchanges information with the APS (if the immobilisation function is enabled).
If, as a result of the exchange, it is determined that access to the vehicle is permitted, the controller continues to perform the engine management functions.
Otherwise, engine operation is blocked.
The controller also performs the system diagnostics function.
It determines the presence of faults in the system elements, switches on the warning lamp and stores in its memory codes designating the nature of the fault and helping the mechanic to carry out the repair.
The engine management system uses a thermoanemometric-type MAF sensor with a frequency characteristic of the digital output signal.
It is located between the air filter and the intake pipe hose.
The MAF sensor signal is a frequency (Hz) signal, the pulse repetition frequency of which depends on the amount of air passing through the sensor (it increases as the air flow rate increases).
The diagnostic device reads the sensor readings as air flow in kilograms per hour.
Throttle position sensors (TPS)
In the system with an electric throttle, two TPS are used.
The TPS are part of the electrically driven throttle body.
The TPS is a potentiometric-type resistor, to one of whose terminals a reference voltage (5 V) from the controller is applied, and to the second — the «earth» from the controller.
From the terminal connected to the moving contact of the potentiometer, the TPS output signal is supplied to the controller.
The controller controls the throttle position by means of the electric drive in accordance with the accelerator pedal position.
From the TPS readings, the controller monitors the throttle position.
When the ignition is switched on, the controller sets the throttle to the pre-start position, the degree of opening of which depends on the coolant temperature.
In the pre-start position of the throttle, the TPS 1 output signal must be within 0.65–0.79 V, the TPS 2 output signal — within 4.21–4.35 V.
If within 15 seconds the engine is not started and the accelerator pedal is not pressed, the controller de-energises the electric drive of the throttle body and the throttle is set to the 7–8 % throttle opening position.
In the de-energised state (LIMP HOME) of the throttle electric drive, the TPS 1 output signal is within 0.80–0.85 V, the TPS 2 output signal — within 4.15–4.20 V.
Then, if no actions are performed within 15 seconds, the mode of checking («learning») the 0-position of the throttle will commence — full closing and opening of the throttle to the pre-start position, and subsequently the throttle electric drive will again go into the de-energised mode.
At any throttle position, the sum of the TPS 1 and TPS 2 signals must be equal to (5±0.1) V.
If a fault occurs in the TPS circuits, the controller de-energises the throttle electric drive, records its code in its memory and switches on the warning lamp.
In this case, the throttle is set to the 7–8 % throttle opening position.
Electronic accelerator pedal (EAP)
On vehicles with an electronic throttle assembly, an electronic accelerator pedal is used, which electrically transmits the accelerator pedal position signal to the controller.
The electronic accelerator pedal is located on a bracket under the driver's right foot.
In the electronic accelerator pedal, two accelerator pedal position sensors (APPS) are used.
The APPS are potentiometric-type resistors, to which a 5 V supply is applied from the controller.
The 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 analogue electrical signal from the EAP, the controller forms a signal for controlling the throttle position.
The APPS output voltage changes in proportion to the depression of the accelerator pedal.
With the accelerator pedal released, the APPS 1 signal must be within 0.46–0.76 V, the APPS 2 signal — within 0.23…0.38 V.
With the accelerator pedal fully depressed, the APPS 1 signal must be within 2.80–3.10 V, the APPS 2 signal — within 1.40…1.55 V.
At any accelerator pedal position, the APPS 1 signal must be twice as large as the APPS 2 signal.
Coolant temperature sensor (CTS)
The sensor is installed in the engine coolant flow, on the outlet pipe of the engine water jacket.
The sensitive element of the coolant temperature sensor is a thermistor, i.e. a resistor whose electrical resistance changes depending on temperature.
A high temperature causes a low resistance, and a low coolant temperature — a high resistance.
The controller supplies a voltage of 5 V to the coolant temperature sensor circuit.
Knock sensor (KS)
The knock sensor (KS) is installed on the cylinder block.
The piezoceramic sensitive element of the KS generates an alternating current voltage signal, the amplitude and frequency of which correspond to the parameters of the engine vibrations.
When knock occurs, the amplitude of vibrations of a certain frequency increases.
The controller then corrects the ignition advance angle to suppress the knock.
Control oxygen sensor (COS)
The most effective reduction in the toxicity of exhaust gases of petrol engines is achieved with a mass ratio of air and fuel in the mixture of (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 with the exhaust gases.
To optimise the composition of the exhaust gases in order to achieve the greatest efficiency of the catalytic converter, closed-loop fuel supply control with feedback on the presence of oxygen in the exhaust gases is used.
Diagnostic oxygen sensor (DOS)
To reduce the content of hydrocarbons, carbon monoxide and nitrogen oxides in the exhaust gases, a catalytic converter is used.
The converter oxidises hydrocarbons and carbon monoxide, as a result of which they are converted into water vapour and carbon dioxide.
The converter also reduces nitrogen from nitrogen oxides.
The controller monitors the redox properties of the converter by analysing the signal of the diagnostic oxygen sensor installed after the converter.
Vehicle speed sensor (VSS)
The vehicle speed sensor emits a pulse signal which informs the controller of the vehicle's speed. The VSS is installed on the input shaft of the transfer gearbox.
When the driving wheels rotate, the VSS generates 6 pulses per metre of vehicle movement.
The controller determines the vehicle speed from the pulse repetition frequency.
Crankshaft position sensor (CKPS)
The crankshaft position sensor is installed on the camshaft drive cover at a distance of about 1±0.4 mm from the tip of the tooth of the trigger disc secured to the engine crankshaft.
The trigger disc is combined with the generator drive pulley and is a gear wheel with 58 teeth arranged at a pitch of 6°, and a «long» recess for synchronisation formed by two missing teeth.
When the middle of the first tooth of the toothed sector of the disc after the «long» recess coincides with the axis of the CKPS, the engine crankshaft is in the position of 114° (19 teeth) before top dead centre of the 1st and 4th cylinders.
When the trigger disc rotates, the magnetic flux in the magnetic circuit of the sensor changes, inducing alternating current voltage pulses in its winding.
The controller determines the position and rotational frequency of the crankshaft from the number and repetition frequency of these pulses and calculates the phase and duration of the control pulses for the injectors and the ignition coil.
Phase sensor (camshaft position sensor)
The phase sensor is installed on a boss of the cylinder head.
The operating principle of the sensor is based on the Hall effect.
There is a special pin on the engine camshaft.
When the pin passes opposite the end face of the sensor, the sensor sends a low-level voltage pulse (about 0 V) to the controller, which corresponds to the position of the No. 1 cylinder piston in the compression stroke.
The phase sensor signal is used by the controller to organise sequential fuel injection in accordance with the engine cylinder firing order.
Brake signal switch
The brake signal switch is part of the brake pedal assembly and is intended to supply the EEMS controller with the corresponding signals about the driver depressing/releasing the brake pedal.
In systems for controlling the throttle by wire (E-gas), the brake pedal switch signals play an important role, since they are used by the safety function of the EEMS controller software.
For this reason, it is very important to ensure that the brake signal switch is always in an operational state.
In the event of non-conformity of its functional switching characteristic, for example, with spontaneous change of the adjustment values specified in the instructions (due to vibrations of the brake pedal, wear of the switch and the pedal assembly), the vehicle engine may go into an emergency operating mode with forcibly reduced power.
Clutch pedal position signal switch
The clutch pedal position signal switch is part of the clutch pedal assembly and is intended to supply the EEMS controller with a signal about the clutch pedal being depressed.
The switch has one group of contacts switching the voltage from terminal «15» of the ignition switch.
With the clutch pedal depressed, the contacts are open.
The clutch pedal position switch signal is used by the EEMS controller software to improve the vehicle's driving characteristics.
