Electronic Digital Petrol Engine Control System (DME)
1 - adsorber
2 - shut-off valve
3 - fuel tank ventilation valve
4 - fuel pressure regulator
5 - injector
6 - pressure transmitter
7 - ignition coil
8 - position sensor
9 - secondary air pump
10 - shut-off valve
11 - air mass meter
12 - control device
13 - throttle sensor
14 - idle speed adjuster
15 - air temperature sensor
16 - exhaust gas recirculation valve
17 - fuel filter
18 - knock sensor
19 - speed sensor
20 - engine temperature sensor
21 - oxygen sensor
22 - diagnostic connector
23 - diagnostic control lamp
24 - differential pressure sensor
25 - fuel pump
The electronic engine management system allows:
- Reduce the content of harmful substances in the exhaust gases by accurately setting the ignition timing in any engine operating conditions.
- To increase the power of the ignition spark on a gasoline engine and, consequently, the reliability of starting and the stability of its operation.
- Self-diagnosis of the engine management system, provides the ability to quickly find faults. The engine management system has a fault memory. If a defect is detected during operation, it is stored in the instrument's memory. With the help of special devices, you can display a list of faults that allows you to eliminate the defect yourself. See also Section Troubleshooting. It is desirable to carry out work in the conditions of a service station.
The engine control unit is a minicomputer with high speed. It, among other things, determines the optimal ignition timing on a gasoline engine, and on a diesel engine, by means of a relay, turns on the glow plugs. In this case, the operation of the control unit is coordinated with other vehicle systems, for example, with the gearbox control system or the anti-theft lock.
Elements of the engine management system retain their high performance for a long time and require virtually no maintenance. Maintenance replacements require only spark plugs. Serious adjustment and repair work requires the use of sophisticated diagnostic tools. Refer to Section Troubleshooting. It is desirable to carry out work in the conditions of service stations.
Correction of the ignition timing on gasoline engines, as part of the maintenance, is not required.
Due to the good starting characteristics of a direct injection diesel engine, preheating is required mainly at temperatures below 0°C.
Information coming from various sensors and commands coming to the executive bodies ensure optimal engine operation in any mode. If the sensors fail, the control unit switches to emergency mode to prevent damage to the engine and allow the vehicle to continue moving. The failure of the sensors should not necessarily be felt as a deterioration in the quality of the engine.
However, no later than the next exhaust gas check date (AU) data about this will be entered in the fault memory of the engine management system.
- The ignition system has no moving parts, and there is no traditional ignition distributor. Each spark plug has its own coil.
- The ignition voltage control system switches off the DME if the voltage is too low (e.g. due to cable damage). In this case, the engine cannot be started. This prevents damage to the catalytic converter.
- The anti-knock control system is used to determine and regulate the optimum ignition timing for each cylinder. If a malfunction occurs in the ignition system, the fuel supply to the corresponding cylinder is cut off.
- The fuel pump relay is located in the relay box above the glove box. The relay supplies current to the fuel pump.
General description of the OBD self-diagnosis system
1. The OBD system includes several diagnostic devices that monitor individual parameters of the toxicity reduction systems and fix the identified failures in the memory of the onboard processor in the form of individual fault codes. The system also checks sensors and actuators, controls vehicle maintenance cycles, provides the ability to store even short-term failures during operation and clear the memory block.
2. All gasoline models described in this manual are equipped with a second generation on-board diagnostic system (OBD-II). The main element of the system is the onboard processor, often called the electronic control module (ECM), or a power unit operation control module (RSM). The PCM is the brain of the engine management system. The initial data is fed to the module from various information sensors and other electronic components (switches, relays, etc.). Based on the analysis of the data coming from the information sensors and in accordance with the basic parameters stored in the processor memory, the PCM generates commands for the operation of various control relays and actuators, thereby adjusting the operating parameters of the engine and ensuring maximum efficiency of its output with minimum fuel consumption. The OBD-II processor memory data is read using a special scanner connected to the 16-pin diagnostic connector for reading the database (DLC), located under the instrument panel on the driver's side of the vehicle, or to the 20-pin connector located on the left in the engine compartment. Refer to section Troubleshooting.
In principle, the fault codes stored in the memory of the self-diagnosis system can be read using a lamp "Check engine".
3. Engine management/emission control system components are subject to a special extended warranty. You should not attempt to independently diagnose PCM failures or replace system components before the expiration of these obligations - contact the specialists of branded service stations.
Information sensors
4. Oxygen sensors (λ probes) - The sensor generates a signal whose amplitude depends on the difference in oxygen content (O2) in engine exhaust gases and outside air before and after the catalytic converter.
5. Crankshaft position sensor (TFR) - The sensor informs the PCM about the position of the crankshaft and the engine speed. This information is used by the processor when determining fuel injection timing and setting the ignition timing.
6. Piston position sensor (CYP) - Based on the analysis of the signals coming from the sensor, the PCM calculates the position of the piston of the first cylinder and uses this information to determine the moments and sequence of fuel injection into the engine's combustion chambers.
7. TDC sensor (TDC) - The signals generated by the sensor are used by the PCM in determining the ignition timing settings at the time of engine start.
8. Engine coolant temperature sensor (EATING) - Based on the information coming from the sensor, the ECM / PCM makes the necessary adjustments to the composition of the air-fuel mixture and the ignition timing, and also monitors the operation of the EGR system.
9. Intake air temperature sensor (IAT) - The PCM uses information from the IAT sensor to make adjustments to fuel flow, ignition timing settings, and to control the operation of the EGR system.
10. Throttle position sensor (TPS) - The sensor is located on the throttle body and connected to the throttle shaft. Based on the amplitude of the TPS signal output, the PCM determines the throttle opening angle (controlled by the driver from the gas pedal) and adjusts the fuel supply to the inlet ports of the combustion chambers accordingly. The failure of the sensor, or the weakening of its fastening, leads to interruptions in injection and violations of the stability of the idle speed.
11. Absolute pressure sensor in the pipeline (IDA) - The sensor monitors variations in the depth of vacuum in the intake manifold associated with changes in crankshaft speed and engine load and converts the information received into an amplitude signal. The PCM uses the information provided by the MAP and IAT sensors to make subtle fuel adjustments.
12. Barometric pressure sensor - The sensor produces an amplitude signal proportional to changes in atmospheric pressure, which is used by the PCM to determine the duration of the fuel injection timings. The sensor is built into the PCM and cannot be serviced individually.
13. Knock sensor - The sensor reacts to changes in the level of vibrations associated with detonations in the engine. Based on the information coming from the sensor, the PCM performs an appropriate adjustment of the ignition timing.
14. Vehicle speed sensor (VSS) - As its name implies, the sensor informs the processor about the current vehicle speed.
15. EGR valve opening sensor - The sensor notifies the PCM of the amount of displacement of the EGR valve plunger. The information received is then used by the processor when controlling the operation of the exhaust gas recirculation system.
16. Fuel tank pressure sensor - The sensor is an integral part of the fuel vapor recovery system (EVAP) and serves to monitor the vapor pressure of gasoline in the tank. Based on the information coming from the sensor, the PCM issues commands to operate the system purge solenoid valves.
17. Sensor-switch of the pressure of the hydraulic power steering system (PSP) - Based on the information coming from the PSP sensor-switch, the PCM provides an increase in idle speed due to the operation of the IAC sensor in order to compensate for the increased engine loads associated with the operation of the power steering during maneuvers.
18. Transmission Sensors - In addition to the data coming from the VSS, the PCM also receives information from sensors placed inside the transmission or connected to it. These sensors include: (A) secondary speed sensor (indigenous) shaft and (b) intermediate shaft speed sensor.
19. Sensor-switch for controlling the engagement of the clutch of the air conditioner - When power is supplied from the battery to the electromagnetic valve of the K / V compressor, the corresponding information signal is sent to the PCM, which regards it as evidence of an increase in the load on the engine and adjusts its idle speed accordingly.
Executive devices
20. Main relay PGM-FI (fuel pump relay) - The PCM activates the fuel pump relay when the ignition key is turned to the START or RUN position. When the ignition is turned on, the activation of the relay provides a pressure rise in the power system. For more information on the main relay, see Chapter Power, injection and exhaust systems.
21. Fuel Injectors - The PCM ensures that each of the injectors is turned on individually in accordance with the established firing order. In addition, the module controls the duration of the opening of the injectors, determined by the width of the control pulse, measured in milliseconds, which determines the amount of fuel injected into the cylinder. More detailed information on the principle of operation of the injection system, replacement and maintenance of injectors is given in Chapter Power, injection and exhaust systems.
22. Ignition control module (ICM) - The module controls the functioning of the ignition coil, determining the required basic advance based on the commands generated by the PCM. On all models of cars considered in the present Management the ICM which is built in the ignition distributor is used, is more detailed in the present Chapter.
23. Idle speed stabilization valve (IAC) - The IAC valve controls the amount of air bypassing the throttle when the throttle is closed or in the idle position. The opening of the valve and the formation of the resulting air flow is controlled by the PCM.
24. Coal canister purge solenoid valve - The valve is an integral element of the fuel vapor recovery system (EVAP) and, triggered by the command of the PCM, releases the fuel vapors accumulated in the adsorber into the intake pipeline in order to burn them during the normal operation of the engine.
25. Carbon canister purge control solenoid - The solenoid is used by the PCM when the OBD-II system checks that the EVAP system is functioning properly.
Reading fault codes
26. If a malfunction is detected that repeats in a row in two trips, the PCM issues a command to turn on the warning lamp mounted in the instrument panel "Check engine", also called the failure indicator. The lamp will continue to burn until the memory of the self-diagnosis system is cleared of the fault codes entered in it (refer to Specifications). Reading fault codes in the OBD-II system can be done in various ways. The main method is to read using the Troubleshooting devices connected to the 16-pin DLC connector of the OBD-II system. Other methods are not available on all models. Flashing code (manufacturer specific and different from codes "R " SAE standard) can be read by lamp "Check engine".
27. Without starting the engine, turn on the ignition, - control lamp "Check engine" should light up, otherwise it should be replaced. After checking the serviceability of the lamp, turn off the ignition again.
Method for reading flashing codes by lamp "Check engine" (available on some models)
28. After switching on the ignition five times within five seconds, fully squeeze and release the accelerator pedal. If the codes of the faults that have occurred are entered in the processor memory, they will start to be sequentially displayed by the control lamp "Check engine" on the dashboard of a car. Read the flashing code.
The lamp waits for 5 seconds, followed by one flash, then a code is issued at intervals of 2.5 seconds between discharges. After the code is issued, the lamp remains on. Repeat the procedure to read subsequent codes. If the first issued code is 1444, 2444 or 4444, no malfunctions are recorded.
Codes 1000 or 2000, issued by one or two flashes and a long pause, and then a constant burning of the lamp, indicate the end of the issuance of the code.
Flashing codes, different from codes "R ", given in Specifications.
Starting the engine automatically terminates access to the diagnostic system.
Clearing the OBD-II Memory
29. When a fault code is entered into the PCM memory, a warning lamp lights up on the car's dashboard "Check engine". The code remains stored in the module's memory.
30. To clear the ECM memory, connect a scanner to the system and select the CLEARING COEDS function from its menu (Deleting codes). Then follow the instructions displayed on the device, or immediately remove the EFI fuse from its socket in the mounting block for 30 seconds. Alternatively, system memory can be cleared by removing the fuse link (the main fuse of the onboard power supply system), installed near the positive battery terminal (see chapter Onboard electrical equipment) (you can also just disconnect the positive wire from the battery).
Please note that clearing the OBD memory by disconnecting the negative cable from the battery will erase the engine settings and cause engine rpm to become unstable for a short time after the initial start.
If your vehicle's stereo system is equipped with a security code, before disconnecting the battery, make sure you have the correct combination to activate the audio system!
Disconnecting the battery also deletes the receiver's favorite radio stations.
To avoid damage to the ECM, disconnect and connect it only with the ignition off!
31. Make sure the system memory is cleared before installing new emission control system components on the engine. If the fault memory is not cleared before starting the system after replacing a failed information sensor, the PCM will enter a new fault code into it. Clearing memory allows the processor to reconfigure to new parameters. In this case, in the first 50 - 20 minutes after the initial start of the engine, some violation of the stability of its revolutions may occur.