The engines installed in Renault Duster vehicles are equipped with an electronic engine management system with distributed fuel injection.
This system ensures compliance with modern emission toxicity and evaporation standards while maintaining high driving qualities and low fuel consumption.
The control device in the system is the electronic control unit (ECU).
Based on the information received from the sensors, the ECU calculates the parameters for regulating fuel injection and controlling the ignition advance angle.
In addition, in accordance with the embedded algorithm, the ECU controls the operation of the electric motor of the engine cooling system fan and the electromagnetic clutch for engaging the air conditioning compressor, performs the self-diagnosis function of the system elements and notifies the driver of any faults that have occurred.
If individual sensors and actuators fail, the ECU activates emergency modes that ensure the engine's operability.
The amount of fuel supplied by the injectors is determined by the duration of the electrical signal from the ECU.
The electronic unit monitors data on the engine's condition, calculates the fuel requirement and determines the necessary duration of fuel supply by the injectors (signal duration).
To increase the amount of fuel supplied, the signal duration is increased, and to decrease the fuel supply, it is reduced.
The engine management system, along with the electronic control unit, includes sensors, actuators, connectors and fuses.
Electronic control unit
The ECU (controller) is connected by electrical wires to all the sensors of the system.
Receiving information from them, the unit performs calculations in accordance with the parameters and control algorithm stored in the memory of the programmable read-only memory (PROM) and controls the system's actuators.
The variant of the program recorded in the PROM memory is designated by a number assigned to this ECU modification.
The control unit detects the fault, identifies and memorises its code, even if the failure is intermittent and disappears (for example, due to a poor contact).
The engine management system fault indicator in the instrument cluster goes out 10 s after the operability of the failed component is restored.
After repair, the fault code stored in the control unit's memory must be erased.
To do this, disconnect the power to the unit for 10 s (remove the fuse of the power circuit of the electronic control unit or disconnect the wire from the negative terminal of the battery).
The unit supplies various sensors and switches of the control system with 5 and 12 V direct current.
Since the electrical resistance of the power circuits is high, the test lamp connected to the system terminals does not light up.
To determine the supply voltage at the ECU terminals, a voltmeter with an internal resistance of at least 10 MΩ should be used.
The electronic control unit controls the immobiliser system. The ECU is not repairable, so in the event of a failure it must be replaced.
The number and brand of electronic components of the engine management system depend on the vehicle's configuration, which powertrain is installed in the vehicle.
The diagrams of the K4M and F4R engine management systems are presented at the end of the article.
The crankshaft position sensor is designed to synchronise the operation of the electronic engine control unit with the angular position of the crankshaft.
The sensor's operation is based on the Hall effect.
In figure 2 — the K4M engine crankshaft sensor.
In figure 3 — the F4R engine crankshaft position sensor.
The sensor is installed in the front part of the clutch housing above the trigger wheel on the flywheel.
The trigger wheel is a toothed wheel.
As the crankshaft rotates, the flywheel teeth change the sensor's magnetic field, inducing alternating current voltage pulses.
The control unit determines the crankshaft speed from the sensor signals and issues pulses to the injectors.
If the sensor fails, the engine cannot be started.
The camshaft position sensor (phase) (only on the F4R engine) of the inductive type is installed in the rear part of the cylinder head.
As the inlet camshaft rotates, the projections on its front journal change the sensor's magnetic field, inducing alternating current voltage pulses.
The sensor signals are used by the ECU to organise sequential fuel injection in accordance with the cylinder firing order, as well as to control the change in valve timing depending on the engine's operating mode.
If a fault occurs in the camshaft position sensor circuit, the electronic unit stores its code in memory and switches on the warning lamp.
The coolant temperature sensor is installed in the water distributor housing of the engine cooling system.
The sensing element of the sensor is a thermistor whose electrical resistance changes inversely proportional to temperature.
At low coolant temperature (−20 °C), the thermistor's resistance is about 15 kΩ; when the temperature rises to +80 °C, the resistance decreases to 320 Ω.
The electronic unit supplies the temperature sensor circuit with a constant "reference voltage".
The sensor signal voltage reaches its maximum value with a cold engine and decreases as it warms up.
Based on the voltage value, the electronic unit determines the engine temperature and takes it into account when calculating the adjustment parameters for injection and ignition.
If the sensor fails or there are faults in its connection circuit, the ECU sets a fault code and memorises it.
An additional thermistor is also installed in the sensor housing to control the coolant temperature gauge in the instrument cluster.
The throttle position sensor is installed only on the K4M engine.
The throttle position sensor is installed on the throttle body housing and is connected to the throttle shaft.
The sensor is a potentiometer, to one end of which the "positive" supply voltage (5 V) is applied, and the other end is connected to "earth".
From the third terminal of the potentiometer (from the slider), the output signal goes to the electronic control unit.
When the throttle is rotated (by action on the control pedal), the voltage at the sensor output changes.
With the throttle closed, it is below 0.5 V. When the throttle opens, the voltage at the sensor output increases; with the throttle fully open, it should be more than 4 V.
By monitoring the sensor output voltage, the ECU corrects the fuel supply depending on the throttle opening angle (i.e. according to the driver's wish).
The throttle position sensor does not require adjustment, since the control unit perceives idle (i.e. full closure of the throttle) as the zero mark.
The control oxygen concentration sensor is used in the feedback injection system and is installed on the exhaust manifold.
Information on the presence of oxygen in the exhaust gases is used to correct the calculations of the injection pulse duration.
The oxygen contained in the exhaust gases reacts with the sensor, creating a potential difference at the sensor output.
It varies approximately from 0.1 V (high oxygen content — lean mixture) to 1 V (low oxygen content — rich mixture).
By monitoring the output voltage of the oxygen concentration sensor, the controller determines which command for correcting the composition of the working mixture to send to the injectors.
If the mixture is lean (low potential difference at the sensor output), the controller gives a command to enrich the mixture; if the mixture is rich (high potential difference) — to lean the mixture.
The lambda probe is a vulnerable sensor in the vehicle's injection system.
Its service life is from 20 to 80 thousand km depending on the quality of the petrol and oil in the engine, and the operating conditions.
According to the factory recommendation, it should be replaced every 75 thousand km of vehicle mileage.
A few fill-ups with leaded petrol can "poison" the sensor electrodes.
If the oxygen concentration sensor is faulty, the ECU switches to a mode in which its voltage is not taken into account for determining the mixture parameters.
The ECU continues to control the mixture composition taking into account the temperature and parameters of other sensors.
The diagnostic oxygen concentration sensor operates on the same principle as the control sensor.
The signal generated by the diagnostic oxygen concentration sensor indicates the presence of oxygen in the exhaust gases after the catalytic converter.
If the catalytic converter is working normally, the readings of the diagnostic sensor will differ significantly from the readings of the control sensor.
The knock sensor is attached to the side part of the cylinder block in the area between cylinders 2 and 3 and detects abnormal vibrations (knocking shocks) in the engine.
The sensing element of the knock sensor is a piezoelectric crystal plate.
During knocking, voltage pulses are generated at the sensor output, which increase with increasing intensity of the knocking shocks.
The electronic unit, based on the sensor signal, regulates the ignition advance to eliminate knocking combustion of the fuel.
Vehicle speed sensor
During operation, the ECU also uses data on the vehicle speed obtained from the speed sensor.
The sensor is installed on the gearbox.
The sensor's operating principle is based on the Hall effect.
The sensor delivers rectangular voltage pulses to the electronic control unit with a frequency proportional to the rotation speed of the driving wheels.
The absolute pressure sensor in the receiver converts the degree of vacuum in the receiver into a change in electrical voltage, by the value of which the ECU sets the engine's operating parameters.
The sensor is installed on the receiver.
The sensor output voltage changes in accordance with the pressure in the intake pipe — from 4.0 V (with the throttle fully open) to 0.79 V (with the throttle closed).
With the engine not running, the control unit determines the atmospheric pressure from the sensor voltage and adapts the injection adjustment parameters to the specific altitude above sea level.
The atmospheric pressure values stored in memory are periodically updated during steady vehicle movement and during full opening of the throttle.
The solenoid valve of the valve timing change system (only on the F4R engine) is installed in the engine cylinder head.
The valve regulates the pressure of the oil supplied to the valve timing actuator installed at the front end of the inlet valve camshaft.
The system performs optimal adjustment of the valve timing, changing them across the entire range of engine speed and load values, which increases power and torque at any speed mode.
When the engine stops, the oil pressure forces the spool of the control valve to move to the position corresponding to the latest valve timing.
The control valve is actuated by the signal of the engine control unit and supplies oil either to the retard chamber or to the advance chamber, with continuous change of the valve timing respectively either towards their advance or towards their retard.
The intake pipe air temperature sensor is of the same design as the coolant temperature sensor.
It also uses a thermistor whose resistance changes depending on temperature. The ECU continuously supplies voltage to the sensor.
The sensor signal voltage is maximum when the air in the intake pipe is cold and decreases as its temperature rises.
Based on the voltage value, the unit makes corrections when calculating the ignition advance angle.
Also, to maintain optimal engine operating modes under different conditions, the ECU uses signals from the clutch pedal position sensor (vehicle with manual gearbox) or automatic gearbox sensors, the brake signal switch, and wheel rotation speed sensors (ABS).
Based on the signals from the clutch pedal position sensor and the brake signal switch, the ECU distinguishes between the pressed and unpressed positions of the pedals.
When the clutch pedal is pressed, the ECU limits the fuel supply to the cylinders.
The diagnostic connector serves to output from the ECU memory the fault codes detected during the operation of the engine management system.
It is located in the cabin, in the glovebox on its rear wall.
The following main engine operating parameters are read through this connector:
- operating mode of the fuel correction system;
- calculated engine load;
- coolant temperature;
- fuel pressure in the supply system;
- air pressure in the intake pipe;
- engine speed;
- vehicle speed (while moving — with a portable scanning device connected);
- ignition advance angle;
- intake air temperature;
- air flow rate;
- throttle position;
- data from the oxygen concentration sensors.
Before removing any components of the fuel injection control system, disconnect the wire from the negative terminal of the battery.
Do not start the engine if the wire terminals on the battery are poorly tightened.
Never disconnect the battery from the vehicle's on-board network while the engine is running.
When charging the battery, disconnect it from the vehicle's on-board network.
Do not expose the ECU to temperatures above 65 °C in the operating state and above 80 °C — in the non-operating state (for example, in a drying chamber).
Do not disconnect wires from the ECU or connect them to it with the ignition switched on.
Before carrying out electric welding work on the vehicle, disconnect the wires from the battery and the wiring harness connectors from the ECU.
Perform all voltage measurements with a digital voltmeter whose internal resistance is at least 10 MΩ.
The electronic components used in the fuel injection system are designed for very low voltage, so they can easily be damaged by electrostatic discharge.
In order to prevent damage to the ECU, do not touch its terminals with your hands.
The diagram of the K4M engine management system is shown in figure 16.
The diagram of the F4R engine management system is shown in figure 17.
