a 2003 annual Shanghai Volkswagen POLO 1.4 L sedan, equipped with BCC engine, matching a five-speed manual transmission, the user break repair vehicles made during acceleration, and in severe flameout.
After receiving the test car was found guilty of vehicle acceleration does break, the acceleration pedal in the end after the vehicle sometimes stall. VAS5051B connection failure diagnostic system for detecting the engine control, the engine control apparatus display unit 10 stores the fault code (Table 1).
Table 1
After the above-described recording the fault code, try to perform clear operation of the fault code, the fault code can be found cleared. But as long as the engine stall phenomenon occurs test, the engine control unit will store the fault code.
The fault code prompt, initial determination is the injector I, the ignition coil of the power supply line or ground line problems. The car engine-related circuit diagram (FIG. 1) can be seen according to the injector, supply of the oxygen sensor are fuse SB25, power SB9, the fuse from the fuel pump relay J17, is located at the ground line and the engine valve operating chamber cover on the left front side member. So I checked the fuse circuit diagram SB9, SB25, after confirming that there is no problem, we decided to check the fuel pump relay J17. Unplug the relay check and found a lot of pins on its scale, suspect the problem lies here, then replace a new fuel pump relay. Installed after the test found no fault symptoms improved, so I decided to check the engine control system associated wiring. Measured over a specific electrical connector dedicated measuring cassette VAG1598 / 31 (FIG. 2), was found in the static line is less than the resistance between 0.4Omega; (including ground), the power supply and the ignition coil, injector and the oxygen sensor ground were also normal.
FIG 1
FIG. 2
The failure diagnostic VAS5051B connected to the vehicle, while reading the data stream side test, the vehicle is still stalled after a few hard acceleration. But in the process of testing found that the vehicle is off, the water temperature gauge and tachometer vehicle will be zero, but no fuel gaugeZero. Normally, when the vehicle is off, since the ignition switch is still turned off and no gear position, the engine will be restarted motoring wheel, so that the pointer 2 table is not zero, the only reasonable explanation is communication between the engine control unit and the control unit interrupts the meter. In order to verify the author’s judgment, the author uses the gateway VAS5051B fault diagnostic testing, results in the fault memory gateway fault found really meaning an engine control unit no communication fault code. After several test found, as long as the vehicle is turned off, the engine control gateway are stored code means without communication failure. If the read data gateway immediately after the flame, the engine control unit and does not communicate a data bus, as long as the ignition switch 1, it will return to normal.
In general, the engine control unit occurs no case where the communication is possible are the following: an engine control unit and the data line between the meter control unit there is a problem, the engine control unit sudden power failure, the engine control unit and damage. Binding to the specific circumstances of the car, it can be ruled out of the first possible cause of the failure. Because as long as the legitimate start, even if the engine control unit and a meter control unit without communication, the vehicle will not stall. In order to determine whether the possible causes of the second vehicle is turned off, the author measured electrical connection box VAG1598 / 31 to the vehicle, and then the pin into the box interior, taking the engine control unit 30 with a multimeter power supply line (red / black), when viewed in the vehicle is off, the power supply control unit of the engine is interrupted. Test found that as long as the vehicle is connected to V.A.G1598 / 31, the vehicle is not stalled.
In accordance with this new discovery, rule out the possibility of damage to the engine control unit. Further analysis, the peripheral measuring cassette V.A.G1598 / 31 wrapped shielding layer thick, its purpose is to prevent electromagnetic interference in the measurement, at a time when the engine returned to normal, can cause electromagnetic interference car flameout? So I decided to check whether the vehicle install other electronic devices (e.g., xenon headlights, MP3, etc.), but after the installation by checking for any device is not found. If no additional installation of the electronic device, the source of interference is likely that in some spark plugs, ignition coils, generators and the electric fan. Accordance with the principles from simple to complex, and in view of the spark plug disassembly more convenient, soI decided to dismantling the spark plug. After the spark plug is removed, by careful observation, the vehicle not using the original car spark plug (FIG. 3). Is it really the spark plug problem? So I got older spark plug 4 spark plugs replace the original car, after the test was found, the part-load conditions or rapid acceleration of the engine will not stall. It seems the problem lies in the spark plugs, spark plug no confirmed resistance, causing interference.
Figure 3
Finally, after the replacement of the spark plugs, test troubleshooting.
Summary: Through repair faults on the car, so I deeply realize that when some difficult fault diagnosis, there are several points must be noted. First, we must carefully observe symptoms, can not lose a small place, such as the instrument of reaction when the car flameout, which played an important role in establishing the later maintenance directions; secondly, to have some of the appropriate equipment, tools understand, such as an external line measurement box VAG1598 / 31 made shielded, so there is a strong anti-jamming capability, which repairs judge also played no small help; third, to open maintenance ideas, not only be limited to maintenance this part, should fully consider other factors, such as fault if the car has been checking the engine control system, can take a long time to repair. In short, for the maintenance of modern vehicles, we must continue to strengthen theoretical knowledge, but you want to fully integrate theory and practice, and focus on the accumulation of experience, thereby improving the overall level of technology.
(Han Kun)