2. I have made several sections about the faults of the throttle collected for many years, for your reference only.
3. If there is anything wrong, please criticize and correct me. Thank you.
4. The following contents mainly talk about some principle analysis and simple analysis of some small cases. Attach a more comprehensive and common case with graphics. See if it meets your requirements. . . Ha ha. .
Inspection methods and examples of electronic throttle system (mainly based on the experience summary of many technicians and their own experience, accumulated over time)
2006-2009
Due to the requirements of environmental protection, the automobile management system adopts electronic throttle from the original oil-gas regulating fuel supply to the EFI engine. The electronic throttle includes throttle, throttle position sensor, control unit, regulator, throttle indicator light and engine ECU. All components used to judge, adjust and monitor the throttle position belong to the electronic throttle system. ?
* * * * 1. Electronic throttle control system?
There is no mechanical connection between the electronic throttle and the accelerator pedal, and the position information of the accelerator pedal is collected by the accelerator pedal position sensor. Drivers hope that acceleration, deceleration or constant speed will not be directly controlled by cables, but indirectly controlled by EPC. There are two potentiometers that output linear voltage in the accelerator pedal sensor. When the driver steps on the accelerator pedal, it drives the sliding resistor to move, and the signal voltage generated by these two potentiometers is transmitted to the engine electronic control unit (ECU). After calculation, ECU drives the positioning motor of the throttle regulator to drive the throttle to rotate, so that the engine can reach the required air intake. This shows that. The degree of stepping on the accelerator pedal is the driver's requirement for engine torque. The position of the accelerator pedal is a set value. The accelerator pedal position sensor is a set value. On the other hand, in the process of engine running, the electronic control unit can directly control EPC without relying on the signal of the accelerator pedal position sensor. ?
The function of the throttle position sensor is to convert the throttle opening into a voltage signal and transmit it to the engine control module and the transmission control module. According to this signal and the intake signal, the control unit timely adjusts the fuel injection quantity to meet the needs of various working conditions of the engine. ?
Take Changan Ford Focus (C307) car as an example. The car uses electronic throttle, and the throttle opening is controlled by PCM. At the same time, in order to detect its implementation, a throttle position sensor is set up, and a closed-loop control system is formed by using the feedback signal of the throttle position sensor. PCM mainly determines throttle opening, ignition time and fuel injection pulse width according to the signal of accelerator pedal position sensor. In order to improve reliability, two accelerator pedal position sensors are installed on the accelerator pedal. If one of the accelerator pedal position sensors fails, PCM will reduce the output power of the engine. At this time, the engine speed can still reach the highest value, but the acceleration performance will be affected. At this time, the driving computer will display "acceleration? Restore "(? Accelerated limiting mode); ?
If two accelerator pedal position sensors fail at the same time, PCM will control the engine speed at 1500 ~ 4000 r/min, and the maximum speed can only reach 56 km/h. If the brake pedal is depressed, the vehicle speed will drop to idle, and if the brake pedal is released, the vehicle speed will increase. At this time, the driving computer shows "speed? Limited? Mode "(speed limit mode). ?
In a word, the electronic throttle system can output a signal reflecting the actual load of the engine through the throttle position sensor and provide it to the electronic control unit (ECU), and can also execute instructions from the ECU to adjust the throttle opening and control the air intake, thereby increasing or decreasing the output torque of the engine and realizing a series of precise adjustments in the whole engine speed and load range. ? The electronic throttle system transmits information through the data bus CAN. Even if the car is equipped with an automatic manual transmission (AMT), the electronic control unit will automatically adjust the engine speed to adapt to the change of vehicle speed when shifting gears, so the shifting process is very smooth, and the driver does not need to change the position of the accelerator pedal frequently. ?
In addition, cars with electronic accelerator and accelerator pedal position sensors are generally not equipped with a cruise control system alone, and the electronic control unit (ECU) can automatically control the accelerator opening according to the signals of the speed sensor, accelerator pedal position sensor and brake switch to realize constant speed driving, so this model has no cruise ECU, cruise switch and accelerator line. ?
* * * Second, the general performance of electronic throttle system disorder?
Generally, cars with electronic throttle are not equipped with engine failure indicator (MIL), and the electronic throttle indicator replaces the function of engine failure indicator. Electronic throttle indicator light (ETC) lights up to inform the driver that the electronic throttle system is out of order, and the throttle is at 8. The engine speed is limited below 3000 r/min, which is a "limping/going home" mode. At this time, you should check the fault code of the engine, and generally need to clean the throttle. ?
The general manifestations of electronic throttle system failures are as follows. ?
(1) Idle jitter or occasional flameout?
Generally, the engine with electronic throttle will cancel the idle speed regulating valve, and EPC will directly control the idle speed. The engine has idling jitter or occasional flameout. If there is nothing wrong with the spark plug, it is mostly caused by the unclean electronic throttle. Cleaning the throttle and making basic settings can generally solve the problem. ? An Elysee 16 valve engine, with electronic throttle, idling normally after starting. 15s or so began to shake, which was caused by the unclean electronic throttle. After cleaning the throttle, troubleshoot. ?
(2) When braking, does the car have "recoil"?
Suitable for EFI engine with electronic throttle (EPC). In order to optimize the control of acceleration performance, the brake switch status signal, gear signal and air conditioning switch signal are specially transmitted to the engine electronic control unit (ECU), and * * * participates in the control of electronic throttle. A Passat B5? 2.0 cars with a mileage of 70,000 kilometers. During normal driving, the EPC light on the dashboard occasionally lights up, and the car appears "recoil" when braking. Clean the throttle and repair the broken exhaust gas recirculation pipe (located behind the throttle). The fault cannot be eliminated. But as long as you press the brake pedal several times in a row, the EPC indicator light will go out. Check the brake switch and find that it is damaged and has abnormal connection. This is because the car is equipped with an electronic throttle. Once the brake switch is turned on, the ECU will instruct to reduce the fuel injection quantity and temporarily reduce the power output of the engine. In this case, the acceleration performance of the engine will obviously deteriorate. When braking, the car appears "recoil" phenomenon, and the EPC light is on. ?
(3) The steering is heavy, and the fault code indicates that CAN communication failed?
A Mercedes-Benz car, equipped with W 140 chassis, with ASR warning light on while driving and heavy steering wheel control. In principle, the failure of ABS/ASR system is not only caused by the abnormality of wheel speed sensor, hydraulic controller and brake switch, but also may be caused by the abnormality of devices outside ABS/ASR system, the most typical of which is electronic throttle. After the electronic throttle breaks down. ABS/ASR control unit CAN't get the accurate throttle opening signal (i.e. engine load), which leads to the abnormal function of ASR. The opening signal of electronic throttle needs to be transmitted through CAN data bus, so ABS/ASR control unit stores the fault information of "CAN bus communication fault" and lights the ASR warning light. ? (4) Is the air conditioning system in a fail-safe state?
Take Volkswagen Magotan as an example. If the electronic throttle valve (J338) fails, including the abnormal throttle position sensors (G 187, G 188), and the throttle valve is too open due to dirt, the engine electronic control unit (J623) will
Considering the excessive load at this time, the cooling fan is instructed to run at a low speed continuously. ?
*** ? Third, the analysis of the reason why the EPC light of Volkswagen car is on?
The EPC indicator light is always on, which is a kind of fault-prone for Volkswagen. There are many reasons that lead to the light of Volkswagen EPC, which can be roughly divided into two categories. ?
One is the self-diagnosis alarm of electronic throttle system. When some parts of the electronic throttle system fail, the EPC light will light up. Components related to self-diagnosis and alarm of electronic throttle system include throttle position sensors (G 187 and G 188), accelerator pedal position sensors (G79 and G 185), engine wiring harness (wiring harness resistance change, poor grounding, etc. ) and EPC indicator light itself. ?
Second, the engine torque control adjustment is out of tolerance. The core function of electronic throttle system is power control. In the process of engine torque control, the engine ECU will compare the actual torque with the target torque, and if the two values exceed the tolerance, it will light the EPC lamp. Components related to torque control include: brake pedal switch, brake bulb, clutch pedal switch, automatic transmission, hydraulic power steering system pressure switch, air conditioning (A/C) pressure switch, electronic cruise control (CCS) switch, etc. ?
Take Volkswagen POLO) 1.4L car as an example, its EPC indicator light is always on, but sometimes no substantial fault can be found. But as long as the fault code is cleared, the EPC indicator light will go out in a short time, and some maintenance personnel just perfunctory customers. The real reason for the failure has not been found. ?
The common reasons for the EPC indicator light on Volkswagen POLO are as follows. ?
1? Small leakage of air intake system, including leakage of crankcase ventilation device, pulling out the oil dipstick or opening the fuel filler cap when the engine is running, etc. If the vacuum leakage is serious, the compensation adjustment made by the engine ECU according to the oxygen sensor signal exceeds the limit allowed by the internal program. The ECU determines that the electronic throttle system is faulty. ?
2? The throttle is dirty. In maintenance practice, dust is the most common cause of electronic throttle system failure. Connect the scan tool. The fault code "17550" will be detected (lower than the limit value of the load record value), or the fault codes "17550" and "1796 1" will appear at the same time (the suction pipe pressure signal ratio of the height sensor is unreliable). At this time, you can clean the throttle, and then perform "0 1-04-060" for basic setting. ?
3? There is a fault in a component or circuit of the electronic throttle system, including an abnormal brake switch, because the brake switch is actually a part of the electronic throttle system. ? 4? Cylinder compression pressure is too low, resulting in "cylinder missing". ?
If you carefully check the above aspects and confirm that there is no problem and the EPC indicator light is still on, you need to refresh the code of the engine electronic control unit-if it was originally "4837" or "4449" (manual gear), it can be changed to "6512"; If it was originally "4838" or "4378" (automatic transmission), it will be changed to "65 13". ?
* * * four. Basic settings of electronic throttle system?
Under the following circumstances, the electronic throttle system needs basic settings: replacing ECU, replacing electronic throttle, cleaning or repairing throttle, downloading ECU, ECU remote coding, etc. ?
After the electronic throttle is cleaned, the basic settings of the throttle must be made so that the ECU can read the information such as the maximum opening and closing position of the throttle. Ensure that the whole system runs well. ?
Elysee car, equipped with 16 valve engine and electronic throttle. After each start, the idle speed starts to be normal, and it will shake after 15s. This phenomenon is often caused by the unclean electronic throttle, so we should start with cleaning the throttle. If there is a lack of a special fault diagnosis instrument, PROXIA, you can manually set the electronic accelerator and accelerator pedal: first, turn the ignition switch to the "M" position and keep it at the "M" position for 30s (do not turn off the ignition switch or step on the accelerator during this period), then turn off the ignition switch and keep it at 15s, so that the electronic control unit (ECU) can remember the accelerator in the memory EEPROM. If the above operation is improper and the manual setting fails, the ECU will not be able to accurately control the throttle opening. The engine will limp. At this time, special scanning tools need to be used for basic settings before the engine can resume normal operation. ?
The basic setting method of Triumph car after cleaning the electronic throttle is: install the battery connection, turn on the ignition switch for 30s, then turn off 15s, and then take out the ignition key. Then do the basic setting of accelerator pedal position. The method is to insert the ignition key without stepping on the accelerator. Turn on the ignition switch, then press the accelerator pedal to the bottom, stop at 1s, release the accelerator pedal, and start the engine. ? Please pay attention to the following two issues when performing the basic settings of the electronic throttle system. ?
① Before cleaning the throttle valve, remove the negative line of the battery to clear the memory value of the original throttle valve in ECU, which can speed up the adaptive process after cleaning. ?
② Peugeot 307 should be set at a coolant temperature below 30℃. A Peugeot 307? A 2.0L car can barely run without stepping on the gas pedal after cleaning the gas pedal. The more you step on the accelerator, the more you can't run. As long as you restart after the flameout, you can run for a certain distance normally. Use a scan tool to perform the basic setting of the throttle. 1 days later, the same phenomenon occurred again, and the engine fault light did not light up. At this time, the basic setting of the throttle should be carried out, but the general diagnostic instrument can't do the basic setting of the electronic throttle of this car, so the original diagnostic instrument must be used for the basic setting of the throttle. Please note that when performing the basic throttle setting, the engine coolant temperature must be below 30℃, and it will take a long time for ECU to learn and adapt. In idle working condition, it is necessary to learn that the cooling liquid temperature reaches 97℃ and the electric fan starts to rotate. If the basic setting is carried out at high temperature, the fault may occur again. If the basic setting is carried out when the coolant temperature is lower than 30℃, the problem still cannot be solved, and the electronic throttle may need to be replaced. ?
* * * Five, several problems that need to be paid attention to when detecting the fault of electronic throttle.
1? The common causes of poor electronic throttle signal are: dirty throttle, no basic setting, poor contact of related lines and low working voltage. ?
2? Generally, the electronic throttle has six terminals. See table 1 for the position of electronic throttle terminal of Chery SQR484F engine. ?
3? The signal voltage of the throttle position sensor (TPS) increases with the increase of throttle opening. Its signal voltage is close to 5V. When reading the data stream of the throttle position sensor (see Table 2), it is necessary to slowly press and release the accelerator pedal, and then observe carefully. Prevent the floor mat from blocking the opening or closing of the throttle valve, resulting in excessive idle speed or insufficient power. ?
4? Don't adjust the air intake too small for dual-fuel vehicles. When some Elysee 16V dual-fuel vehicles use liquefied petroleum gas, the fault light lights up, and the fault code is read as "electronic throttle fault". Replace the throttle, but it doesn't work. However, after the fault code was cleared and changed to burning gasoline, the fault light was no longer on, indicating that the fault was caused by burning liquefied petroleum gas. This situation is often caused by adjusting the intake volume of LPG too small. The driver lowered the air intake to reduce fuel consumption. Save operating costs, but the final result may not be worth the loss. Because the mixture is too thin, it burns slowly. After one working cycle is over, the next working cycle is still burning. At the beginning of a new cycle, the intake valve is opened, and the flame with incomplete combustion will rush out from the intake valve, resulting in "backfire". The energy of tempering will cause the throttle to shake abnormally, so the fault code of electronic throttle will appear. Frequent "tempering" will also lead to deflagration, which will lead to early damage of valves, spark plugs, cylinder pads, cylinder heads, intake manifolds and air cleaner housings. This calculation is really not worth the loss. Therefore, dual-fuel vehicles should not blindly adjust the air intake too small to avoid a series of adverse consequences. ?
5? For Bora 1.8T vehicles (with electronic accelerator), if the accelerator pedal is pressed to the bottom for a long time, the engine electronic control unit will lack the grounding signal. The fault phenomenon is that the accelerator pedal does not respond (the engine can't speed up), and the EPC light on the dashboard lights up to store the fault information of the accelerator pedal position sensor (G79, G 185). This is a special fault of the electronic throttle system of Bora 1.8T car. The solution is to replace the accelerator pedal position sensor and engine ECU, and then match them.
A Jetta car has unstable power operation and deviation. After inspection, it was found that the throttle valve needed cleaning. Considering that there are still some steps and difficulties (matching) in cleaning this car, I will briefly talk about the process now, hoping to give you some hints.
Tools: carburetor cleaner, carp pliers, crew cut screwdriver, hexagon socket set, flashlight, wet paper towel (dust removal cloth for paint is the best. Hehe, it won't lose hair, and the size is quite suitable)
Open the hood and loosen it. No ability, four things are deducted at the same time. The position in the red box below is: throttle body.
Unplug the electric plug of the air filter pipe.
Loosen the retaining spring clip between the air filter tube (hereinafter referred to as G) and the air filter box. Need to clamp and expand hard. When it expands to a certain extent, the spring clip can be moved to the plastic pipe of the air filter box in the direction of the arrow, and the connecting part of G and the air filter box can be separated by a slight pull.
Please pay special attention to the location of the two most difficult spring clips.
If you want to remove G, you should pay attention to a "hidden" pipe connected to it at this time. When disassembling, please note that it is located under the rubber pipe connecting the oil filler. Unplug! Pipes that need to be pulled out are marked with chalk lines. Please refer to. ? At this point, the tube g can be completely removed. At this time, you can see the inside of the throttle body.
Unscrew 4 throttle fixing screws with No.5 Allen key. It should be noted that when screwing the last screw, leave a space for holding the throttle valve with one hand to avoid falling.
.................................
....................？
.
When the last screw is unscrewed, the throttle can be moved downward. Now you can see the backyard of the throttle.
Clean the throttle. Wipe carefully before and after. Depending on the cleanliness, you can wipe off the dirt before and after the throttle diaphragm with a wet towel (or a rag for painting). If it is dirty, spray it on a wet paper towel (rag) with carburetor cleaner. Until it is clean.
Finally, be sure to pair up. About collocation. Now many detectors can be matched, such as Dr. Che and 43 1. You can also use 505 1 software and VAG-COM line. The specific method can be Baidu.
? Attention: In a certain period of time, it is beneficial to carry out proper throttle cleaning and maintenance according to the mileage, environment and condition of the vehicle. If the smoothness of air intake is hindered by being too dirty, ECU will increase the throttle opening. ? And this larger angle than a clean throttle will be recorded in the memory of ECU. ? The next time the owner starts the car, this angle will be read and acted on the throttle blade. ?
? Under the above circumstances, if you clean the throttle thoroughly and it doesn't match, then under the same working conditions, the intake resistance is reduced and the intake air volume is too large. At this time, there will be so-called idle instability and so on. ? So to make a match, it should be called throttle initialization, and the term is "restore factory settings". ? When the throttle valve is restored to the factory setting, its opening under certain working conditions will definitely be smaller than that of the dirty throttle valve. So, from another angle, it is not difficult to understand why we need to match.