Electronic control unit

Fig. 10-13. Scheme of system of injection: 1 — the fuel tank; 2 — an electrogasoline pump with the fuel level sensor; 3 — the giving highway; 4 — the drain highway; 5 — the fuel filter; 6 — an inlet pipe with an electric heater; 7 — pressure regulator; 8 — the air temperature sensor; 9 — the engine; 10 — a final branch pipe of the cooling system; 11 — the sensor of temperature of cooling liquid; 12 — the idling regulator; 13 — the sector of the drive of a butterfly valve; 14 — a nozzle; 15 — the unit of the central injection; 16 — the relay of a heater of an inlet pipe; 17 — the air filter; 18 — the sensor of provision of a butterfly valve; 19 — the sensor of concentration of oxygen; 20 — a final collector; 21 — the sensor of absolute pressure; 22 — a depression selection tube; 23 — the transmission; 24 — catalytic converter; 25 — the speed sensor; 26 — a control lamp of "CHECK ENGINE"; 27 — an electronic control unit; 28 — the relay of inclusion of an electrogasoline pump

The Electronic Control Unit (ECU) of 27 (fig. 10-13) located under a ware box is the operating center of system of injection of fuel. It continuously processes information from various sensors and operates the systems influencing toxicity of the fulfilled gases and operational indicators of the car.
The following information comes to the control unit:
— about situation and frequency of rotation of a bent shaft;
— about the absolute pressure of air;
— about air temperature;
— about temperature of cooling liquid;
— about the provision of a butterfly valve;
— about the content of oxygen in the fulfilled gases;
— about tension in onboard network of the car;
— about car speed;
— about request for turning on of the conditioner (if it is established on the car);
— a signal about an octane potentiometer.
On the basis of the obtained information the block operates the following systems and devices:
— fuel feeding (nozzle and electrogasoline pump);
— system of ignition;
— idling regulator;
— electroheating of an inlet pipe;
— adsorber of system of catching of vapors of gasoline;
— engine cooling system fan;
— the conditioner compressor coupling (if it is on the car);
— system of diagnostics.
The control unit includes output chains (a nozzle, various relays, etc.) by their short circuit on weight via output transistors of the control unit. The only exception — a chain of the relay of the fuel pump. Only on a winding of this EBU relay gives tension of +12 Century.
The control unit has the built-in system of diagnostics. He can distinguish malfunctions in work of system, warning about them the driver through a control lamp of "CHECK ENGINE". Besides, it stores the diagnostic codes specifying areas of malfunction to help experts with carrying out repair.
Memory. In an electronic control unit there are two types of memory: operational memory device (OMD) and once programmable read-only memory (PROM).
The operational memory device is "notebook" of an electronic control unit. The EBU microprocessor uses it for temporary storage of the measured parameters for calculations and for the interim information. The microprocessor can enter as required data in it or read out them.
The chip of the RAM is mounted on the EBU printed circuit board. This memory is volatile and demands uninterrupted food for preservation. At interruption in supply of food the diagnostic codes of malfunctions and settlement data which are contained in the RAM are erased.
Programmable read-only memory. In PPZU there is the general program which contains the sequence of working teams (control algorithms) and various calibration information. This information represents data of management of injection, ignition, idling, etc. which depend on the mass of the car, type and engine capacity, on the transfer relations of transmission and other factors. PPZU call still the memory device of calibrations.

Fig. 10-14. Electronic control unit: 1 — an electronic control unit; 2 — the programmable read-only memory (PROM); 3 — a cover

Contents of PPZU cannot be changed after programming. This memory does not need food for saving information which is written down in it which is not erased at power off, i.e. this memory is non-volatile. PPZU is established in a nest on a payment of EBU (fig. 10-14) and can be taken out from EBU and be replaced.
PPZU individually for each complete set of the car though on different models of cars the same unified EBU can be applied. Therefore when replacing PPZU it is important to establish the correct number of model and complete set of the car. And when replacing defective EBU it is necessary to leave former PPZU (if it is serviceable).