2. A catalytic converter is installed on all models. The oxygen sensor before the converter is included in the feedback of the engine management system. In addition, there is a fuel vapor recovery system controlled by a BEU. The engine management system ensures that the most modern requirements for the composition of exhaust gases are met. The operation of the part of the system that controls the ignition is described in chapter 5B. The following 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. Fuel pressure is maintained at a predetermined level by a regulator located in the fuel rail (M43TU and M52TU engines) or built into the fuel filter (engines N42 and M54). When the pressure in the fuel system increases beyond the optimum value, the excess fuel returns back to the tank.
4. The engine control system, in addition to the BEU, includes the following sensors.
- A) The heated film air mass sensor will give the BEU information about the amount and temperature of the air supplied to the engine.
- b) Throttle position sensor (engine M43TU) informs the ECU about the position of the throttle valve and the speed of its closing or opening.
- V) Sensor (And) coolant temperature informs the ECU of the engine temperature.
- G) The crankshaft position sensor informs the ECU of the speed and position of the crankshaft at any given time.
- d) Sensor (And) camshaft position (ov) give BEU information about the current position of the camshafts.
- e) Sensor (And) oxygen informs the BEU about the oxygen content in the exhaust gases (This will be discussed in more detail in Chapter 4B).
- and) The speed sensor informs the ECU about the speed of the car on the road.
- h) The inlet air temperature sensor informs the ECU about the temperature of the air entering the engine (engines M52TU and M54).
- And) The oil temperature sensor informs the ECU of the oil temperature in the engine.
5. The signals of all the listed sensors are analyzed by the BEU. which, based on this information, calculates the fuel supply corresponding to the current operating conditions of the engine. The BEU controls the fuel supply by changing the width of the pulse applied to the opening of the injectors. BEU constantly regulates the composition of the mixture, leaning or enriching it, and thus maintains the composition of the mixture, which is optimal for the current mode of engine operation - starting, warming up, idling, acceleration, constant speed, etc.
6. When the throttle is fully closed. BEU switches to idle control using an air valve that regulates the air supply through the channel bypassing the throttle.
7. BEU manages exhaust gas and fuel vapor control systems. These systems are described in chapter 4B.
8. All engines have an intake manifold with an adjustable path length (DISA system). The length of the path is regulated by a throttle valve in the intake manifold, depending on the speed and engine load. Thanks to this system, torque is increased at low and medium engine speeds. The damper is actuated by a vacuum actuator located under the manifold.
9. If an abnormal signal is received from any sensor in the BEU, the BEU switches to the limited controllability mode. It starts ignoring the wrong signal and replaces it with the pre-set value, which allows the motor to continue running, albeit with less efficiency. When switching to this mode, a fault code is entered in the memory of the BEU.
10. If a malfunction in the control system is suspected, the car should be shown to the dealer or workshop specialists as soon as possible. Using a trouble code reader, they will check the system. The code reader is simply connected to the diagnostic socket of the control system. The 16-pin OBD connector is located under the bezel, while the system connector can be located either on the right side of the engine compartment or under the bezel (see fig. 10.2, a, b).