In order for multiple electronic control units to communicate with each other, these units are connected by a high-speed CAN data bus (see chapter 5). The CAN bus consists of two lines, which reduces the amount of wiring. Each control unit can simultaneously transmit and receive data, however, each specific unit reads only the data it needs from the CAN bus.
The principles of organizing fuel and air supply systems are described in Section 1.
A description of the sensors and components used by the engine management system to reduce exhaust emissions is provided in Part B.
Information from the sensors listed below and some other sensors is used by the ECM to generate control voltages for the final control elements to ensure optimal engine performance in any situation. If some sensors fail, the control unit switches to the emergency program mode in order to exclude possible damage to the engine and ensure the further movement of the car.
The engine control unit (ECM) determines the optimal ignition timing (on petrol models) and injection, as well as the amount of injected fuel in coordination with other vehicle systems. On petrol models, the high spark voltage from the ECM is generated by the ignition module.
crankshaft position sensor (TFR) gives the engine control unit information about the number of revolutions of the crankshaft and its exact position. This information is used to determine injection timing. The TFR sensor is located on the rear side of the engine and works on the basis of the Hall effect, scanning the teeth of the rotor mounted on the crankshaft. One of the teeth is missing, and the detection of this gap indicates that the crankshaft is in the position corresponding to the TDC position of the compression stroke of the piston of cylinder # 1. If the CKP sensor fails, the engine will shut down and will not start.
Camshaft position sensor (SMR) works similarly to the SKR sensor. by scanning the toothed rotor at the end of the camshaft. The CMP sensor, together with the CKP sensor, is used to determine the TDC of the piston of the first cylinder and determine the injection sequence.
Knock sensor (KS only on petrol models) screwed into the cylinder block, prevents the occurrence of shock combustion of fuel. As a result, the ignition timing is kept at the detonation limit, which ensures a better use of the energy of the fuel and thus a reduction in fuel consumption. If there is no signal or if the KS signal disappears, knock control is disabled and the ECM switches to an operating mode based on base values that are far from the actual knock limit values. In this case, knocking combustion can damage the engine.
The engine coolant temperature information from the ECT sensor is used by the ECM to calculate fuel injection timing and duration, which varies with engine temperature.
The accelerator pedal module consists of an accelerator pedal, support bracket, springs, a stub axle with two magnets, and a dual accelerator position sensor (APP). In the accelerator pedal module with the function "Kickdown" (on models with DSG) an additional compression spring with a stop is installed between the gas pedal and the support bracket so that the driver feels the moment the function is activated "Kickdown". The principle of operation of the APP sensor is non-contact, based on the Hall sensor. The ECM uses the signal from the APP sensor to calculate the amount of fuel injected. If the APP sensor fails, the engine idles at an increased speed and does not respond to pressing the gas pedal.
Clutch position sensors (on models with manual transmission) and brakes track the position of the respective pedals to ensure the operation of the tempostat and transmission. The transmission neutral position sensor is used to enable the engine to start on models with DSG.
The engine oil level and temperature sensor is designed for a more flexible oil change interval. The sensor information is used to determine the level and quality of the oil. When determining the quality of the oil, the deposition of soot particles in the oil is also taken into account. The soot deposition parameter is determined empirically and stored in the corresponding characteristic.