However, the method used to fast and accurate diagnosis, more awareness is not uniform, there was the blind pursuit of high-end equipment and the tendency to rely on, or even completely ignore other effective methods, which is an incorrect concept .
my opinion, for those of us people.
diagnosis in the modern automobile, As little as possible with the equipment, the use of fast, simple equipment, is to ensure diagnostic method. In general, the
one experience diagnosis - based on the experience of diagnostic methods and professional standards regardless of how
automotive technology advances, many common failures can still be judged by experience. Phenomenon is not only a failure caused by a common fault only when the need for further diagnostics to help determine the point of failure. Therefore, I do not agree with the so-called
the following situations, often encountered in practice. Fault with the manufacturer, model, grade not so much the vast majority of cases do not need to enable diagnostic procedure, and use the experience to be an immediate solution (do not rule out a few exceptions): vehicle acceleration sl
uggish, due to circuit common block or pump some of the work of non-performing; hard acceleration when the and loss of gear, the common cause for the transmission oil is dirty, causing the filter block; some of the vehicles repaired by maintenance staff, the idle, air conditioning engine flameout, but the reaction of the normal idle speed valve, the common reason for premature ignition time .
symptoms such as these abound, but as a
mentioned above, That is simple, open air conditioning, ECU order to improve the idle speed, idle valve open while also advance the ignition timing, idle speed to compensate for the delayed reaction of the valve and the air. Caused by premature ignition time of installation, open air, the ignition time earlier, leading to engine flameout. And this in many books and not mentioned. Therefore, relying on books or the use of advanced equipment like decoding instrument, often with such simple causes of failure are difficult to find. At this point, experience a few minutes we will solve the problem, books, and advanced equipment and carry us away, maybe a few days can not find fault.
generate automatic transmission shift shock, no gear shift or other fault slip phenomenon, different models shown are not the same phenomenon. Sometimes experience will tell us - As long as we have some automatic transmission oil expertise, this truth is self-evident.
, of course, the empirical diagnostics, requires experience and expertise. By the accumulated experience and professional knowledge by study, not many shortcuts. If there is a shortcut, then it is more communication with others (including conversations, meetings, reading magazines and other methods), the experience of others into their own experience to accelerate their accumulation of experience; learn the knowledge of the shortcut is Select mentor, the most appropriate books supplemented to avoid deep into the vast sea of books.
Second, the original car computer information law - the original car-based method of data communication failure
beyond the common range in the car, and the experience of diagnosis and do nothing, read the trouble code or data flow should be the best choice. More convenient diagnostic computer connection, the use of computer information to determine the original car with a scientific and accurate fault. But in some cases the original car is more general computer information (such as a cylinder working poor), need to determine the specific failure or mechanical failure are electronic control system failure.
computer diagnostic equipment to read the information inside the computer the original car, no more than two cases:
1. fault or a fault code lights
most cases directly in accordance with fault code troubleshooting However, note the following two points:
⑴ determine the fault is referred to by the code elements are the cause of, or caused by the relevant line (or even caused by the computer), it normally takes with a multimeter, test tools help detect light and the like.
⑵ analysis of the causes of fault codes. If fault code display mixture concentrated (dilute) or mixing ratio disorders, oxygen sensor signal malfunction, and even simultaneous dense mixture and dilute mixture of two fault codes. In this general and contradictory situation, the analysis of the causes of fault codes and to develop the best, further assessment of the program is required. To disorders in terms of mixing ratio, fault diagnosis must consider two aspects: First, mechanical failure, including hydraulic malfunction, fuel leaks, leak, oxygen sensor contamination, fire, lack of compression pressure; Second, electronic control system failure, including air flow meter is damaged, inaccurate temperature, oxygen sensor is damaged, damaged computers and so on.
2. fault or no fault light does not need to read the code
general data flow, and sometimes need to do match, the encoding of the type of operation. Specific operations in the automotive repair manual or computer diagnostic manual, presentations, very easy to learn. The key is reading the data stream, it should be good at analysis. Because the manual is often given in the standard data, but did not give reasons for the deviation of the data, you need to diagnose people use their brains. First, select key according to symptoms observed in the data; the second is to analyze the causes of data bias. For example, high fuel consumption, lack of motivation, focusing on the observed data are: fuel injection pulse width, air flow, temperature, throttle, oxygen sensors. Here are a few cases for all tastes:
⑴ a car idling and acceleration smoke, read the data stream that: the supply voltage 9.8V, but the multimeter to measure computer power supply pins are for the 12V. For the computer, the fault remains.
Comment: The power relay contact erosion, resulting in contact resistance is too large. Engine work, the work current, the voltage loss increases at the relay contacts,
You look over your father and mother , so the voltage drop available to the computer; measured with a multimeter, the engine does not work, there is no current, there is no voltage loss, so the measurement results show that the voltage normal.
⑵ a vehicle cold start problems, data flow shows high water temperature, after inspection, after changing the water temperature sensor failure, the data remains.
Comment: water temperature signal of a voltage divider circuit there is a problem, as long as the temperature signal generation to understand the principle, it is not difficult to judge (of course the premise of the normal signal power 5V).
⑶ a vehicle can automatically shift, but the late shift and there is impact.
Comment: only 2 main signal shift, can shift the normal speed signal is illustrated, it should focus on examination of the throttle signal is too large.
⑷ for speeding in a car can not be blocked.
Comment: In addition to shifting the valve, overspeed switch signal, the engine water temperature, etc. Do not forget to block the effects of speeding, this may cause for the computer, for automatic transmission assembly, and other unnecessary operations.
Third, detection and diagnosis method - based on a common method of testing equipment for testing
general, this method is not efficient, the former two methods have been used since the choice of last resort.
the method commonly used test equipment including lights, multimeter, thermometer, current clamp, oscilloscope, engine Analyzer, oil pressure meter, vacuum gauge, tank pressure gauge, etc., based on symptoms or failure code, data flow using the targeted choice.
1. test light, multimeter: measuring power,
mbt shoes discounts, grounding, signal voltage, component resistance,
Shox Torch, lines. For those unfamiliar with the models, we should first see the schematic, which is crucial.
2. hydraulic table, vacuum table, cylinder pressure gauge, etc.: used to determine mechanical problems. Disassembly operation due to the need, generally in determining the electronic control system is normal, and the most common possibilities (rule of thumb) has been ruled out when used.
3. oscilloscope: the waveform used to measure the sensor, fuel injector waveform, ignition waveform, the other solenoid valve waveform generator voltage waveform, the waveform signal between the computer and so on. How you can quickly learn, but to read the waveform is not an ordinary mechanic can do, need to go through specialized training. However, the situation need to use the oscilloscope is not much, only fault in the car appeared difficult, but rely on conventional methods can not resolve before choosing an oscilloscope.
4. Engine Analyzer (such as EA3000): can be used for power balance of each cylinder, the cylinder compression pressure balance analysis, and the ignition waveform, intake manifold vacuum waveform, the waveform engine oil pressure, electronic control system signal waveform, such as testing, and exhaust gas analyzer connected, but also can work with the engine exhaust emission analysis. The device is a high level of professional diagnosis or professional researchers who design, is not available to the general mechanics use. Therefore, do not require all of the mechanics will use a medium to large automotive repair business, as long as one or two professionals to be able to use enough. Operation is not difficult to use, but rather on the analysis of the results. Of course, not difficult to learn not to the extent of repair, but no need to call all learn, because the real need to use the opportunity Engine Analyzer is too low.
5. Signal Simulator: crankshaft and camshaft can be used for analog signals, analog voltage signal, frequency signal simulation, switching signal simulation. In some cases, can really improve the diagnostic rate, but the use of analog signals to the attention of the signal with the match between the original car, otherwise the computer may cause the failure of the original car.
IV replacement method - based on the direct replacement of the suspect parts and components in an attempt to approach
although from the perspective of conservation,
ugg slippers sale, or maintenance personnel from a professional point of view, only to determine if a parts and components failures do exist, and can not be repaired before deciding to replace. However, the high-paced modern society, the economic value not only by a zero, reflected in part their own, but by the time and efficiency, reflected in a combination of factors. This is in the taxi business as well as the maintenance of important people in the car repair process is particularly prominent. Therefore, the replacement method can not be sniffed, in the form of high-paced society should be promoted even, but the key issue is the professionalism and experience. Replacement is the purpose to achieve fast, to see to judge the accuracy of the fault. Once inaccurate, it will self-defeating.
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【He Jishun Chi
⑶ a vehicle can automatically shift
Linear Mode
