The main elements of the power system

The coolant temperature sensor (ECT)

The coolant temperature sensor is located in the channel of the coolant of the cylinder head (Fig. 2.136). This resistor whose resistance varies with the temperature of the cooling fluid flowing around the probe. If the coolant temperature is low, the sensor resistance is high, and vice versa.

The engine control unit 50 times per second checks the voltage of the coolant temperature sensor and uses this information to adjust the pulse width of opening of the fuel nozzles and adjust the ignition timing. Lockable If the temperature is low, the engine control unit enriches the fuel mixture and ignition timing increases, and vice versa.

1. Remove the engine coolant temperature sensor from the intake manifold.

2. Immerse yourself in the hot water temperature sensitive part of the coolant temperature sensor, measure the resistance (Fig. 2.137). The resistance values ??at the terminals of the sensor according to the temperature shown in Table. 2.22.

Table 2.22

The resistance at the contacts of the sensor depending on the coolant temperature

3. If the measured resistance is not correct, replace the coolant temperature sensor.

4. Apply sealant LOCTITE 962T or equivalent to the threaded part of the sensor.

5. Replace the coolant temperature sensor and tighten it to a torque of 20-40 Nm.

6. Securely connect to the sensor connector.

The gauge of absolute pressure in the intake manifold (MAP) sensor and the intake air temperature (IAT)

The main element of the pressure sensor in the intake manifold is attached to the membrane with her ??thin wire (Fig. 2.138). Depending on the pressure membrane flexes, wires attached to it, stretched, changing its resistance. The engine control unit applies a voltage to 5V absolute pressure sensor in the intake manifold and monitors the voltage drop across the sensor. As the pressure decreases the output signal (voltage) of the sensor increases. Signal pressure sensor in the intake manifold adjusts the fuel delivery and ignition timing.

Intake air temperature (IAT), a built-in absolute pressure sensor in the intake manifold - is based sensor resistor, which determines the temperature of the intake air. Based on information about the temperature of the intake air temperature sensor ECU determines the required amount of fuel injected.

1. Measure the voltage between terminals "1" and "4" sensor connector in the intake manifold. The voltages at the terminals of the pressure sensor in the intake manifold depending upon the measurement conditions shown in Table. 2.23.

2. If the measured voltage is not correct, replace the gauge of absolute pressure in the intake manifold.

Table 2.23

The voltage at the terminals of the pressure sensor in the intake manifold, depending on the measurement conditions

Meter of air (MAF)

After passing through the air cleaner enters the engine passes through the air flow meter air-heated wire element (Fig. 2.139).

At idle when the throttle is closed, only a small amount of air passes by the heated wire element that causes a slight cooling. When you press the accelerator pedal and a larger opening angle of the throttle by wire element passes more air, and the degree of cooling increases.

Due to the reduction in temperature changes the resistance wire element and therewith flowing through it an electric current. By changing the current control unit determines the amount of air entering the engine.

Air flow meter with a wire element contains no moving parts, so it is the aerodynamic resistance within the intake tract slightly.

1. If the engine accidentally stops, rotate the crankshaft starter and shake wire air mass meter. If the motor stops, check the connection pin air mass meter.

2. If the output voltage of the sensor air mass meter when the ignition is different from zero, check the air mass meter and the engine control unit.

3. If the engine can run at idle, even when the output voltage of the air mass meter is not correct, check the following:

- Perturbation of the air flow meter in mass airflow;

- To remove the duct clogged air filter;

- Incomplete combustion of air-fuel mixture in the cylinders of the engine;

- Condition of spark ignition coils and fuel injectors;

- Leakage of air from the intake manifold.

4. Even if the mass air flow meter is working properly, check its position.

Intake air temperature sensor (IAT)

Intake air temperature sensor disposed on the air filter, - a sensor whose resistance varies with temperature. According to information coming from this sensor, the ECU will adjust the required amount of fuel injected. In addition to the air flow meter transmits a signal to the control unit to determine the motor load.

1. Measure the voltage between terminals "1" and "2" sensor connector intake air temperature when the ignition or the engine running. The voltages at the terminals of the sensor according to the temperature shown in Table. 2.24.

2. If the measured voltage is not correct, replace the intake air temperature sensor.

Table 2.24

The voltage at the terminals of the intake air temperature sensor based on temperature

Throttle Position Sensor

The throttle position sensor mounted on the side of the throttle assembly and rigidly connected to the axis of the throttle valve (see. Fig. 2.138).

Sensor - a rotary variable resistor that is rotated together with the throttle shaft and changes resistance depending on the angle of rotation of the damper. The sensor detects the position of the throttle at the moment, and then informs the control unit, which uses this information to adjust the idling speed, ignition and selects calculates the injection time.

Throttle position sensor also includes a switch to the idle position.

1. Remove the pin from the throttle position sensor.

2. Measure the resistance between terminal "4" (connection with "weight") and contact "1" (power sensor) on engines DOHC, and on the engines V6 - between terminal "2" (connection with "weight") and contact "1 "(sensor supply).

Resistance - 3.5-6.5 kW.

3. Connect the analog ohmmeter between terminal "4" (connection with "weight") and contact "2" (sensor output) on engines DOHC, on engines V6 - between terminal "2" (connection with "weight") and contact " 3 '(sensor output signal).

4. Slowly adjust the position of the throttle from idle to full opening position and make sure that the resistance gradually changes according to the angle of the throttle opening.

5. If the resistance of the sensor is not correct or does not change smoothly, replace it.

Tightening torque screws Throttle Position Sensor - 1.5-2.5 Nm.

Actuator idle speed control

The actuator control idle speed - a mechanism with double winding, with separate driver stage power amplifier in the engine control unit (see. Fig. 2.138). It maintains constant engine speed of the engine at idle, regardless of the engine temperature and the air conditioner, which consumes a lot of energy. Depending on the duty cycle balance of magnetic forces of the two coils will result in different directions of the magnetic forces, which in turn lead to different positions of the actuator. Bypass the actuator is parallel to the throttle assembly.

1. Remove the pin from the actuator control idle speed.

2. Measure the resistance between the contacts "1" and "2", and between "2" and "3".

Rated resistance:

- Between terminals "2" and "3" - 10,5-14,0 Ohm;

- Between contacts "1" and "3" - 10,0-12,5 Ohm.

3. Connect the connector to the actuator control idle speed.

Heated oxygen sensors

To achieve a high degree of purification of exhaust gas from harmful emissions (CO, NOx, and CH), three-way catalyst is used, but for more effective use of its air-fuel ratio must be maintained at a certain level. The power supply system of the engine with the catalytic converter - a closed type, that is based on the signal from the oxygen concentration sensor installed in the exhaust system, the control unit constantly optimizes fuel ratio.

Heated oxygen concentration sensor detects the oxygen concentration in the exhaust gas, and then converts it into a voltage, and transmits the engine control unit. This induces the sensor output voltage around 1 V, when the mixture is richer, and the voltage equal to zero when the mixture was poorer (higher oxygen content in the exhaust gases). Based on this signal, the engine control unit controls the fuel injection, so the composition of the mixture is maintained as close as possible to the theoretical values. An oxygen concentration sensor mounted heating element, which reduces the time of actuation of the sensor in operation.

1. If heated in oxygen concentration sensor is faulty, the amount of harmful substances in exhaust gas may increase.

2. If during the inspection it was found that single heated oxygen concentration sensor is serviceable, but the output voltage does not correspond to the desired value, check the following components related to the control system richness:

- The fuel injectors;

- Intake manifold air leaks;

- Condition of the air flow meter, the canister purge valve and the coolant temperature sensor.

Connect a digital voltmeter to terminals "1" and "2" connector.

By increasing the speed of the crankshaft of the engine, measure the output voltage of the oxygen concentration sensor, which is in the acceleration mode in a car with DOHC engine should be more than 0.6 V, the vehicle with the engine V6 - 4,0-4,8 V.

If the sensor output voltage is not correct, replace the sensor.

Tightening torque sensor - 40-50 Nm.

Camshaft position sensor

Camshaft position sensor determines the TDC cylinder ?��1 and ?��4 (Fig. 2.140). Its signal is transmitted to the engine control unit to determine the sequence of fuel injection.

If the operation of the camshaft sensor is broken, the fuel injection will not occur in the desired sequence, which may lead to stop of the engine or it will run rough idling or will not increase the engine speed.

Sensor crankshaft angle

Sensor crank angle determines the position of the piston of each cylinder and converts it into an electric pulse (Fig. 2.141). The signal voltage of the sensor is transmitted to the control unit engine, based on which it determines the speed and position of the crankshaft. Based on the signal of the sensor unit calculates the injection and ignition timing.

1. If you feel shaking motion of the engine or the engine suddenly stops, shake sensor wires. If this is the cause of stopping the engine, check the connection of the sensor connector contacts.

2. If the tachometer indicates zero when cranking the engine, check the sensor crank angle, the state of the toothed belt camshaft drive and the ignition system.

3. If the engine is idling, even if the signal is outside of the desired range of values, check the following:

- Coolant temperature sensor;

- The engine speed of the engine idling.

Fuel injectors

Fuel injectors - is controlled by a solenoid valve. When the solenoid fuel injector is energized (pulse) opens the needle valve nozzle. Fuel under pressure passes through the nozzle and mixes with air entering the engine cylinders. The engine control unit controls ignition timing and pulse width, and then sends pulses to the fuel injector based on information from various sensors. The unit uses the information in the crankshaft position sensor to determine when the pulse to the fuel injector. Furthermore, to determine the duration of the pulse supplied to the fuel injectors, the temperature data recorded coolant temperature, intake air amount and the air throttle position.

The fuel injectors inject fuel in accordance with signals from the ECU. The volume of injected fuel determined by the time during which the solenoid valve is activated fuel injector.

1. If a hot engine starts with difficulty, check the compression and tightness of the fuel injectors.

2. If the nozzle does not work when cranking the engine, and check the following circuit elements:

- Condition of the circuit supplying power to the engine control unit or circuit connection with "weight";

- Serviceability of the relay adjusting fuel injection;

- Condition of the crankshaft position sensor and camshaft.

3. If the engine condition is not changed after the fuel injection into the cylinders stopped one by one, check the following:

- The fuel injectors and wires;

- Spark plugs and high voltage wires;

- The engine compression.

4. If the injection system is working, and the opening of the fuel injector is not correct, the following reasons:

- Unstable ignition of the fuel-air mixture in the cylinders of the engine (spark plugs, ignition coil, low compression in the cylinders of the engine, and so on. D.);

- The weakening of landing the EGR valve.

Check the operation of the fuel injector

1. With the engine idling stethoscope check the fuel injectors for the presence of the clicking. Make sure that as the speed of the crankshaft of the engine sound appears at shorter intervals.

2. In the absence of a stethoscope, check job nozzles finger. If the vibration is not felt, check the connector wires, fuel injector or a signal supplied to the injector engine control unit.

Measurement of winding resistance fuel injector

1. Unplug the connector from the fuel injector.

2. Measure the resistance between the two contacts on the nozzle.

Rated resistance - 13-16 ohms at 20 ?� C.

3. Reconnect the connector to the fuel injector.

Purge solenoid valve filter

This valve load control controls the flow of air coming from the filter system for collecting fuel vapors.

Knock sensor

The knock sensor is attached to the side of the cylinder block to define a detonation in the engine cylinders. The vibration of the cylinder block is transmitted as a pressure to the piezoelectric element. This vibratory pressure is converted into a voltage signal that is transmitted to the engine control unit. If knocking occurs in the engine cylinders, the control unit shifts the ignition timing to the delay side.

1. Remove the pin from the knock sensor.

2. Measure the resistance between terminals "2" and "3" connector.

Nominal impedance knock sensor - about 5 milliohms at 20 ?� C.

3. If the resistance is much greater than the nominal, replace the knock sensor.

Tightening torque knock sensor - 16-28 Nm.

4. Measure the capacitance between the terminals "2" and "3" connector.

The nominal capacity of the knock sensor - 800-1600 pF.

The pressure sensor (PSP) assisted steering

Sensor fluid pressure in the power steering system determines the load steering system and converts it into signals low / high level transmitted engine control unit, which is based on these signals, controls the engine speed to idle.