Gasoline engines installed on Mazda 6 cars are equipped with an electronic engine control system with distributed fuel injection.
This system ensures compliance with modern standards on the toxicity of emissions and evaporation of harmful substances, while maintaining high driving performance and low fuel consumption
The control device in the system is an electronic control unit (ECU, controller).
Based on the information received by the recoilers, the ECU calculates the parameters of fuel injection regulation and ignition timing angle control.
In addition, in accordance with the algorithm laid down, the ECU controls the operation of the electric motor of the fan of the engine cooling system and the electromagnetic clutch of the air conditioner compressor, performs the function of self-diagnosis of system elements and notifies the driver of malfunctions.
In case of failure of individual sensors and actuators, the ECU switches on 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 the engine status data, calculates the fuel demand and determines the required duration of fuel supply by injectors (signal duration).
To increase the amount of fuel supplied, the duration of the signal increases, and to reduce the fuel supply, it decreases.
The engine control system, along with the electronic control unit, includes sensors, actuators, connectors and fuses.
Electronic control unit (ECU) is connected by electrical wires to all 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 a programmable permanent storage device (PPZU), and controls the system"s actuators.
The version of the program recorded in the memory of the CPU is indicated by the number assigned to this modification of the ECU
The control unit detects the fault, identifies and remembers its code, even if the failure is unstable and disappears (for example, due to poor contact).
The engine control system malfunction alarm in the instrument cluster goes out 10 seconds after the failed node is restored to working capacity.
After repair, the fault code stored in the memory of the control unit must be erased.
To do this, turn off the power supply of the unit for 10 seconds (remove the fuse of the power supply circuit of the electronic control unit or disconnect the wire from the terminal "minus" of the battery).
The unit supplies DC voltage of 5 and 12V to various sensors and switches of the control system.
Since the electrical resistance of the power supply circuits is high, the indicator lamp connected to the system terminals does not light up.
To determine the supply voltage at the terminals of the ECU, a voltmeter with an internal resistance of at least 10 mOhm should be used.
The ECU is not suitable for repair, in case of failure it must be replaced.
The diagnostic connector is used to output fault codes detected during operation of the engine management system from the ECU memory.
The diagnostic connector is located in the car interior on the left side of the instrument panel under the steering wheel.
A scanning device that reads fault codes can be connected to the diagnostic connector.
The inductive type crankshaft position sensor is designed to synchronize the operation of the electronic control unit with the TDC of the pistons of the 1st and 4th cylinders and the angular position of the crankshaft.
The sensor is installed in the rear of the engine opposite the driving teeth on the flywheel. The driving teeth are made on the surface of the flywheel at regular intervals.
One tooth is missing to create a synchronization pulse ("reference" pulse), which is necessary to coordinate the operation of the control unit with the TDC of the pistons in the 1st and 4th cylinders.
When the crankshaft rotates, the teeth change the magnetic field of the sensor, inducing AC voltage pulses.
The control unit uses the sensor signals to determine the speed of rotation of the crankshaft and outputs pulses to the injectors.
If the sensor fails, the engine cannot be started.
The camshaft position sensor (phase sensor) of the inductive type determines the TDC of the compression stroke of the piston of the 1st cylinder.
The signal from the sensor is used by the electronic control unit and serves to organize phased fuel injection in accordance with the order of operation of the cylinders.
If a malfunction occurs in the circuit of any of the sensors, the ECU enters its code into its memory and turns on the signal lamp.
The coolant temperature sensor is installed in the coolant distributor housing at the rear of the engine.
The sensor"s sensing element is a thermistor whose electrical resistance varies inversely with temperature.
At a low temperature of the coolant (-40 ° C), the resistance of the thermistor is about 100 kOhm, when the temperature rises to +130 ° C, it decreases to 70 ohms.
The electronic unit feeds the temperature sensor circuit with a constant "reference" voltage.
The voltage of the sensor signal is maximum on a cold engine and decreases as it warms up.
According to the voltage value, the electronic unit determines the engine temperature and takes it into account when calculating the adjustment parameters of injection and ignition.
In case of sensor failure or violations in the circuit of its connection, the ECU sets the fault code and remembers it.
In addition to the above, the sensor indirectly serves as a sensor of the coolant temperature indicator in the instrument cluster.
According to the information from this sensor, the electronic engine control unit changes the position of the pointer arrow.
The combined absolute pressure and temperature sensor of the intake air in the intake manifold is made in the form of a variable resistor sensitive to pressure changes.
It records the pressure change in the intake manifold in accordance with changes in the load and engine speed.
Depending on the information received from the sensor, the ECU registers the amount of fuel injected and the ignition timing angle.
The throttle position sensor is made in one piece with the throttle assembly cover.
The sensor is a potentiometer, one end of which is supplied with a "plus" supply voltage (5 V), and the other end is connected to the "mass".
From the third output of the potentiometer (from the slider) there is an output signal to the electronic control unit.
When the throttle valve turns (due to the impact on the control pedal), the voltage at the sensor output changes.
When the throttle is closed, it is below 0.5 volts. When the flap opens, the voltage at the sensor output increases, with the flap fully open, it should be more than 4 volts.
By monitoring the output voltage of the sensor, the ECU adjusts the fuel supply depending on the throttle opening angle (i.e. at the request of the driver).
The throttle position sensor does not require adjustment, since the control unit perceives idling (i.e. full throttle closure) as a zero mark.
The mass flow sensor and the intake air temperature mounted on the nozzle of the air filter housing is a very important sensor in the electronic engine control system.
Based on its signal, the electronic engine control unit determines the cyclic filling of the cylinders and eventually corrects the duration of the nozzle opening pulse and the ignition timing angle.
Oxygen concentration sensors (lambda probes) are screwed into the threaded holes of the catalytic converter and the receiving pipe.
Two oxygen concentration sensors are installed on Mazda 6 cars:
- a control sensor designed to control the composition of the fuel-air mixture (at the entrance to the neutralizer);
is a diagnostic sensor designed to evaluate the efficiency of the neutralizer (at the output).
In the metal bulb of the sensor there is a galvanic element washed by the exhaust gas flow.
Depending on the oxygen content in the exhaust gases, the voltage of the sensor signal changes as a result of the combustion of the fuel-air mixture.
The sensors vary in parameters and have different markings. If at least one of the oxygen concentration sensors is faulty, the toxicity of the exhaust gases may increase dramatically, and fuel consumption will increase.
For the convenience of replacement, the sensors differ in the color of the pads. The sensor wiring harness at the entrance to the neutralizer (control) is green, and at the exit from the neutralizer (diagnostic) is purple.
Information from each sensor enters the control unit in the form of low (from 0.1 V) and high (up to 0.9 V) level signals.
When the signal is low, the control unit receives information about the high oxygen content. A high level signal indicates a low oxygen content in the exhaust gases.
By constantly monitoring the voltage of the sensor signal, the control unit corrects the amount of fuel injected by the injectors.
At a low signal level of the sensor at the input to the neutralizer (poor fuel-air mixture), the amount of fuel supplied increases, at a high signal level (rich mixture) - decreases.
If the difference between the sensor signal levels at the input and output of the neutralizer is less than the values allowed under this operating mode, the control unit identifies a malfunction of the catalytic converter.
The detonation sensor, attached to the upper part of the cylinder block in the zone between the 2nd and 3rd cylinders, detects abnormal vibrations (detonation shocks) in the engine.
The sensitive element of the detonation sensor is a piezocrystalline plate.
During detonation, voltage pulses are generated at the sensor output, which increase with increasing intensity of detonation shocks. The ECU adjusts the ignition timing according to the sensor signal to eliminate detonation flashes of fuel.
During operation, the ECU also uses the vehicle speed data received from the anti-lock system control unit (ABS).
Before removing any components of the fuel injection control system, disconnect the wire from the "minus" terminal of the battery.
Do not start the engine if the wire tips on the battery are poorly tightened.
Never disconnect the battery pack from the vehicle"s on-board mains 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 working condition and above 80 °C in non-working condition (for example, in a drying chamber). It is necessary to remove the ECU from the car if this temperature is exceeded.
Do not disconnect from the ECU and do not attach wires to it when the ignition is on. Before carrying out electric welding work on the car, disconnect the wires from the battery and the wiring harness pads from the ECU.
Perform all voltage measurements with a digital voltmeter with an internal resistance of at least 10 mOhm.
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.
In all cases, a special scanner is required to diagnose the engine control system, therefore, if a system malfunction occurs, contact a specialized service.