2. All models are equipped with a catalytic converter. The oxygen sensor before the converter is included in the feedback loop of the engine management system. In addition, there is a fuel vapor recovery system, which operates under the control of the electronic control unit. The engine management system ensures compliance with the most modern requirements for the composition of exhaust gases. The operation of the part of the system that controls ignition is described in Chapter 5B. Below is a description of the operation of the part of the system that controls fuel injection.
3. The fuel pump, immersed in the fuel tank, supplies fuel to the filter and then to the fuel rail. The fuel pressure is maintained at a given level by a regulator located in the fuel rail (engines M43TU and M52TU) or built into the fuel filter (n42 and M54 engines). When the pressure in the fuel system increases beyond the optimum value, excess fuel returns back to the tank.
4. The engine management system, in addition to the electronic control unit, includes the following sensors.
- a) The hot film air flow sensor will provide the ECU with information about the amount and temperature of air supplied to the engine.
- b) Throttle position sensor (m43TU engine) informs the ECU about the position of the throttle valve and the speed at which it closes or opens.
- c) The coolant temperature sensor informs the ECU of the engine temperature.
- d) The crankshaft position sensor informs the ECU of the speed and position of the crankshaft at any given time.
- d) The camshaft position sensor provides the ECU with information about the current position of the camshafts.
- e) The oxygen sensor informs the ECU about the oxygen content in the exhaust gases (more details about this will be discussed in Chapter 4B).
- g) The speed sensor informs the ECU about the speed of the vehicle on the road.
- c) The air inlet temperature sensor informs the ECU about the temperature of the air entering the engine (engines M52TU and M54).
- i) The oil temperature sensor informs the ECU of the oil temperature in the engine.
5. The signals from all the listed sensors are analyzed by the ECU, which, based on this information, calculates the fuel supply corresponding to the current engine operating conditions. The ECU controls the fuel supply by changing the pulse width supplied to open the injectors. The ECU constantly regulates the mixture composition, leaning or enriching it, and thus maintains the mixture composition optimal for the current engine operating mode - starting, warming up, idling, acceleration, constant speed, etc.
6. When the throttle valve is completely closed. The ECU switches to idle control using the air valve, which regulates the air supply through the channel bypassing the throttle valve.
7. The ECU controls the exhaust gas and fuel vapor management systems. These systems are described in Chapter 4B.
8. All engines are equipped with an intake manifold with adjustable tract length (dISA system). The length of the tract is regulated by a throttle valve in the intake manifold depending on the speed and engine load. Thanks to this system, the torque at low and medium engine speeds is increased. The valve is driven by a vacuum actuator located under the manifold.
9. If an abnormal signal comes from any sensor to the ECU, the ECU goes into a limited controllability mode. It starts to ignore the incorrect signal and replaces it with a preset value, which allows the engine to continue to operate, although with less efficiency. When switching to this mode, a malfunction code is entered into the ECU memory.
10. If a fault is suspected in the control system, the car should be shown to the dealer or service station specialists as soon as possible. Using a trouble code reader, they will check the system. The code reader is simply connected to the diagnostic connector of the control system. The 16-pin on-board diagnostic connector is located under the front panel, while the system connector can be located either in the right corner of the engine compartment or under the front panel (see fig. 10.2,a,b).