In modern automobiles, the use of sensors is becoming more and more common. In order to facilitate the maintenance of the engine, this paper introduces more than a dozen common engine sensor detection methods as follows.
The intake manifold pressure sensor is a very important sensor in the D-type fuel injection system. Its function is to convert the pressure change in the intake manifold into a voltage signal. The control computer (ECU) determines the entry according to the signal and the engine speed (provided by the engine speed sensor installed in the distributor). The amount of air in the cylinder.
1. installation parts and wiring terminals.
Because the manifold pressure sensor has an amplifier circuit inside, it needs three wires: power line, ground line and signal output line. They have three terminals on the terminal, namely, power terminal (Vcc), ground terminal (E) and signal output terminal (PIM), three terminals through the wire connector and the guidance and control computer ECU. To be connected.
To reduce the vibration of electronic components in intake manifold pressure transducers, it is usually mounted on a trusted vehicle with relatively low vibration and above the intake manifold to prevent air from flowing into the pressure transducer, and the intake manifold pressure transducer receives the intake manifold pressure from the bottom to prevent it. The signal sensor part is not contaminated, so the intake pipe gas collected from the intake manifold near the throttle through rubber hose is connected from the lower end of the manifold pressure sensor.
2. Monomer detection
(1) appearance inspection
During inspection, the manifold pressure sensor can be found on the car simply by finding the rubber tube from the intake manifold near the throttle. Firstly, under the condition of semi-locked ignition, check the intake manifold pressure sensor wire connector whether the connection is good rubber hose is off, and then start the engine to check whether the rubber hose is not tightly sealed and leakage phenomenon.
(2) instrument test
A. Turn on the ignition switch (ON) test the voltage value between connection terminal Vcc and E2 with the DC voltage block (DCV-20) of the multimeter. The voltage value is the value of the power supply voltage added by ECU to the manifold pressure sensor. The normal value should be between 4.5-5.5 V. If the value is not correct, the battery voltage or the connection between conductors should be checked. Problems may also arise when controlling computer ECU.
B, connect the ignition switch (ON), and remove the vacuum rubber hose from the intake manifold pressure sensor. When the intake port of the intake manifold pressure sensor is connected with the atmosphere, the output voltage signal of the test line terminal (the voltage between PIM and E2) is between 3.3 V and 3.9 V. Common rail test bench.If the output voltage is too high or too low, the intake pipe pressure sensor should be replaced.
C. Turn on the ignition switch (ON) position, remove the vacuum rubber hose on the intake manifold pressure sensor, apply the following different negative pressure (vacuum degree) to the intake port of the manifold pressure sensor with the hand-held direct air pump, and test the voltage between the terminal transmission voltage signal PIM and the ground line E2 while applying the pressure. The voltage value should follow the applied negative pressure. The growth is linear. Otherwise, the signal detection circuit in the sensor should be replaced. For example, the normal data of the 2JZ-GE engine of the Crown 3.0 car are shown in the table.
Air flow sensor is one of the most important sensors in L-type (mass flow) electronic fuel injection engine. It measures the air flow into the cylinder and is an important energy data of the basic ignition advance angle. Therefore, the fault detection and analysis of air flow sensor monomer is very important for EFI engine. At present, there are many kinds of air flow sensors, but according to the different measuring principles, they can be divided into three types: blade type, eddy current type and hot wire type. Because of the differences in the structure of the three kinds of sensors, their individual fault detection is different, and are analyzed separately.
1. Leaf plate type air flow sensor
(1) installation location and terminal
The vane type air flow sensor is installed between the throttle body of the air filter to accurately measure the air volume of the suction engine.
In the engine control, in order to accurately obtain the air mass flow required by the engine, it is necessary to consider the density of the air. The density of the air varies with the temperature and pressure of the air. In order to prevent the quality deviation caused by the change of the air temperature, an air inlet temperature sensor is installed in the air flowmeter. Therefore, there is an air temperature signal (THA) output on the connecting terminal of the vane type air flow sensor (the case of the inlet temperature sensor will be analyzed separately).
In order to ensure that the electric fuel pump of the EFI engine works only when the engine is running and prevent misoperation, the control switch of the electric fuel pump is installed in the vane type air flow sensor. Only when the engine is rotating, when there is air flowing into the air flow sensor, the fuel pump switch is closed, thus starting the fuel pump truck operation. When the engine stops turning, even if the ignition switch is turned on (ON) the pump does not work, so there is an electric fuel pump control signal (FC, E1) output on the wiring terminal of the vane type air flow sensor.
The vane-type air flow sensor has seven terminals connected to the control computer through a wire connector, which are FC and E1 terminals for fuel pump control, THA terminals for outputting air temperature signals, E2 terminals for inputting power supply voltage to the sensor and grounding VC, and ECU terminals for computer control. The VB and VS terminals of the inlet and outlet signals (using double-signal output and VB/VS terminal voltage ratio in ECU to analyze the inlet can eliminate the misalignment of the measured inlet signals due to the fluctuation of the power supply voltage VC)
(2) sensor monomer detection
First check whether the conductor is in good contact with the wiring (switch off the ignition switch when plugging in the sensor) and then check whether the air flow sensor shell is broken and whether there is leakage at the connection with the intake pipe.Common rail test bench. (When the engine is running, you can use a piece of paper to close to the air flow sensor to see if there is suction, if there is, air leakage, should be After the engine stops running, turn off the ignition switch (OFF position) and pull out the blade plate manually to see if the base swings smoothly and if there is a phenomenon of sticking, if there is, it should be replaced.
Before switching on the ignition, do not start the engine, and then measure the input and output voltage of the vane type air flow sensor on the corresponding terminal of the control computer ECU (in order to judge its performance characteristics), should comply with the following table:
|VC-E2||Measuring plate at any opening||4-6|
|VS-E2||Measuring board close||3.7-4.3|
|Measuring board open||0.2-0.5|
Turn off the ignition switch (OFF position) and unplug the wire connector of the vane type air flow sensor to measure the resistance of the corresponding terminal. If the resistance does not match, the air flow sensor should be replaced.
|Measuring terminal||Leaf plate position||Standard resistance(KΩ)|
|E1-FC||From start to full closed||0.02-1.0|
2. Eddy current air flow sensor
(1) installation part and connection terminal
Swirl air flow sensors are usually integrated with the air filter housing and connected to the throttle body on the intake manifold.
In order to facilitate the timely detection of intake temperature, swirl air flow sensor is equipped with intake temperature, sensor, control computer ECU according to the intake temperature signal (THA), to modify the air density with temperature changes, therefore, swirl air flow sensor terminal terminal temperature signal (THA) and intake. The ground terminal (E1) of the gas temperature sensor.
In order to ensure the normal operation of the internal circuit of the eddy current air flow sensor, the working voltage is input to the sensor by controlling the computer ECU. The signal terminal is VC and the grounding terminal is E2.
The output signal terminals of the eddy current air flow sensor are often represented by the "KS" symbol.
(2) monomer detection
In this paper, we take the reflective mirror type eddy current air flow sensor on the IUE-EF engine of Toyota Lexus LS400 as an example to test the sub-board of the sensor.
First turn on the ignition switch (ON) position, but do not start the engine, then measure the ECU to the sensor power supply voltage, that is, the voltage between the conductor connector terminal VC and E2 ground terminal, the normal value is: 4.5-5.5V.
When the above voltage is normal, the voltage between the output signal terminal KS and the ground terminal E2 of the eddy current air flow sensor can be measured. The first step is to turn on the ignition switch when the engine does not start, KS and E2 voltage values are 4.5-5.5V. The second step is to start the engine at idle speed (1000 rad / min), the voltage between KS and E2 terminal is pulse voltage, and the voltage value is between 0.2 and 0.4 V.
3. Hot wire air flow sensor
(1) installation part and wiring terminal
The hot-wire air flow sensor is installed between the air filter and the main intake pipe of the engine, and the back end is the throttle body.
Because the hotline is installed in the intake pipe, the surface of the hotline will be contaminated by the dust in the air after a period of use, which will cause the deviation of the output signal of the air flow sensor and reduce its measurement accuracy. To overcome this problem, a sensor thermal self-cleaning circuit is set up in the integrated circuit, which makes the sensor shut down every time. When the engine controls the computer ECU, it controls the circuit to convey a limit voltage value to the hotline, so that the hotline can be heated to about 1000 degrees quickly to remove the dirt on it, so as to achieve self-cleaning. Therefore, in the terminal of the wire connector of the hotline air flow sensor, there is a terminal in which the ECU inputs the self-cleaning signal.
Because the hot wire type air flow sensor needs a large current, its power supply is not through the control of the computer ECU, but directly from the battery (of course through the relay) so the terminal terminal has a battery power supply terminal, but also correspondingly increased through the control of the computer internal iron terminal. It serves as the terminal of the heating circuit of the hotline.Common rail test bench.
The hot-wire air flow sensor transmits the voltage signal of hot-wire rheology change and the voltage signal of cold-wire resistance change to ECU through two terminals, which is equivalent to THA signal of intake temperature sensor.
In addition to the iron terminal mentioned above, the hot wire air flow sensor has another iron terminal which is built by controlling the inside of the computer ECU. It is the iron terminal of the signal circuit inside the sensor.
(2) monomer detection
The test data of hotline air flow sensor are slightly different because of different vehicle types, but the test methods are basically the same.
Inspection of self cleaning function of hotline
The self-cleaning function signal terminal of the vehicle is represented by "F" and the dust-proof net of the air filter and air flow sensor is removed without pulling out the wire connector. Start the engine and accelerate to more than 2,500 rad/min, then close the ignition opening (OFF) position, at this point from the dust screen inlet to see if the hot wire can automatically burn red, (after closing the ignition switch for 5 seconds, the hot wire can be heated to (1000 degrees) and lasts for about 1 seconds. If there is no such phenomenon, the air flow sensor hotline self-cleaning function fails, if the "F" terminal wiring is good, the need to replace the air flow meter.Common rail test bench.
Output signal characteristic check
On the premise of turning off the OFF position, unplug the conductor connector of the air flow sensor, remove the air flow sensor assembly, and measure the output signal. Before measuring the output signal, add the battery voltage between the sensor battery voltage input terminal "E" and the iron terminal "D" (battery positive electrode connection E) The negative level is connected to D), and then the output voltage value of the sensor is measured according to the following steps.
1. Measure the static output signal value, and use the voltmeter to measure the voltage value between the voltage output signal terminal "B" and the iron terminal "D". The normal value is 1.6 + 0.5V. If the voltage does not match, the air flow sensor should be replaced.
2. Hot air is blown into the air flowmeter with a mouth or a hairdryer, and the voltage between the "B" terminal and the "D" terminal should be measured at the same time. The voltage should be kept between 2.0-4.0V when blowing, otherwise it should be replaced.
3. Blow hot air and cold air to the air flow sensor with the hairdryer and the fan respectively, and measure the voltage value between "A" and "D" of the cold wire signal terminal. The fluctuation should be suitable, otherwise the air flow sensor should be replaced