Analysis on the cause of abnormal flameout of the

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Analysis on the causes of abnormal flameout of electronic control engine shift

Abstract: through the fault of lzw6360bi1 electronic control engine which caused the abnormal flameout of the vehicle when shifting into idle working condition due to the wrong connection of harness, the red fork troubleshooting method is used to analyze in detail the judgment idea of finding the fault and the principle of high-frequency signal interference caused by the change of voltage and current between harness connections

Keywords: lzw6360bi1; Electronic control engine; Abnormal flameout; Signal interference; ECU is always powered on

when it is displayed, the query word is highlighted. In the maintenance of modern automotive electronic control engine, some seemingly incomprehensible fault phenomena are often encountered. Due to the influence of traditional inertia thinking of fault diagnosis, maintenance operators often feel at a loss, and it is difficult to consider and judge from the correct thinking direction, so as to quickly and accurately find the real fault source. Based on the examples in product development, from the perspective of after-sales maintenance and problem solving, this paper discusses the application of general GMS problem red fork through continuous research and Analysis on the causes of abnormal flameout of electronic control engine shift of lzw6360bi1 Euro III emission standard( ×) Troubleshooting method, using oscillograph, digital recorder and X431 electronic control detector to analyze the interference of voltage signal, so as to realize the rapid and accurate diagnosis of some difficult faults of electronic control engine

in order to continuously improve the product quality and performance of the whole vehicle and meet more stringent relevant emission regulations and noise control requirements, SAIC General Motors Wuling Automobile Co., Ltd. upgraded the engine electronic control system of the best-selling model lzw6360bi1 minibus in June, 2005. This model is matched with lj462qei1 electronic control engine and adopts Delphi mt20u (Delphi II generation) electronic control management system. See Table 1 for the main differences before and after the upgrade of the electronic control system

I. fault phenomenon

after the road test of 30000 km for the first batch of test sample vehicles in May 2005, all the tested performances meet the product design requirements, and there are no abnormalities. However, in the subsequent use of a small number of specific test users, there were continuous feedbacks that the engine was easy to shut down when shifting a red light or coasting in neutral. The fault performance condition has certain particularity: the vehicle can start normally, there are no other abnormal conditions during driving, the engine fault indicator light is not on before flameout, and there is no fault code. 1. The amorphous material motor can start and start immediately after flameout, and other performances such as power, acceleration, economy, etc. are normal. Moreover, the fault performance is intermittent during an indefinite period, and the fault phenomenon of short-term test run is difficult to reproduce

II. Fault diagnosis

in view of the particularity of the performance of this fault, the relevant departments of SGMW launched the general GMS Red Cross( ×) The troubleshooting method is to analyze and study the problem

according to the Red Cross( ×) The operation requirements of the troubleshooting method are to first define the problem, list the possible causes of the problem and make a red cross according to the relevant causes( ×) Eliminate, and then list the remaining possible causes as the next round of problem definition, so as to gradually narrow the scope of the root cause of the problem, so as to achieve the purpose of solving the problem efficiently and quickly

(I) problem definition 1

shut down when the throttle decelerates and shifts into idle speed. The specific analysis of the reasons for the flameout when the throttle decelerates and shifts into idle speed is shown in Table 1

(II) problem definition 2

electrical part fault analysis of electrical part is shown in Table 2

(III) problem definition 3

the electronic control system is interfered by high-frequency signals. The analysis of the interference of the electronic control system by high-frequency signals is shown in Table 3

after many times of troubleshooting and gradually reducing the scope of the root cause of the problem, it was found from the engine harness of the faulty vehicle that the corresponding lines of pin17 and pin18 pins of the normally energized power supply entering the ECU were two red wires ecu17#, ecu18#, as shown in Figure 1

disassemble the engine harness assembly, find the connection point along the two red normally connected power wires towards the power interface, and find that they are connected with the power lines of ignition coil and fuel injector, as shown in Figure 2

the engine harness of the first batch of test sample vehicles is a manual sample line. After disassembly and analysis, it is found that the corresponding ecu17#, ecu18# normally on power lines are connected separately, as shown in Figure 3

III. fault analysis

the primary power line of the ignition coil in the engine harness assembly is connected with the ecu17 #, ecu18 # normally on power line entering the ECU, causing the high-frequency voltage signal generated during the operation of the ignition coil to interfere with the idle stepper motor, and the electronic control system misoperates, resulting in the reduction of the control steps of the idle stepper motor, and the working condition when the vehicle shifts into idle speed is the most sensitive point of the idle stepper motor, So it led to the failure. The following analysis is based on the comparison of the test results with oscillograph and data recorder

the oscillogram recording diagram of idle stepping motor signal and ignition coil ignition voltage signal of the faulty vehicle is shown in Figure 4. The oscillogram recording diagram of the idle step motor signal and ignition coil ignition voltage signal of the test sample vehicle is shown in Figure 5

from the comparison of the above two oscillographic records, it can be clearly shown that some alloys such as 2XXX series alloy with high alloying, 7xxx series alloy, 5xxx series alloy with Mg content greater than 6%, aluminum lithium alloy, aluminum scandium alloy, etc. can not be produced, let alone mass produced. The signal amplitude is large and dense, which greatly exceeds the anti-interference capacity of the electronic control system, leading to the occurrence of faults

IV. troubleshooting and verification

replacing the correct engine harness produced in mass on 8 faulty vehicles can not meet the market demand. After continuous tracking of 20000 km road test, no fault recurrence of abnormal gear shift and flameout is found

the electronic control management system used by the automotive electronic control engine is often sensitive to electromagnetic signal interference, and the high-frequency electromagnetic signals generated by the ignition coil and fuel injector during operation can form a strong circuit interference. Therefore, whether in product development or application and maintenance, we must pay attention to the independent reliability of the ECU's normally connected power line and avoid connecting with the power control line of other components. (end)

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