A 2004 Shanghai Volkswagen Passat 1.8GSi sedan, equipped with Volkswagen AG401N 4-speed electronic control automatic transmission, the user reflects the impact of the transmission gear shift shock symptoms. After the car we carried out road test to determine the car transmission the following faults: ① into the forward gear and reverse gear impact. ② into the forward gear transmission power, the transmission will be issued within a long time similar to the friction of the sound. ③2-3 block the impact of serious. ④ high-speed car when the engine speed and the corresponding speed does not match, obviously feel the engine speed is high, the feeling of the lack of a block, should be the torque converter lock clutch work poor. ⑤ As the speed increases, the noise inside the transmission will increase.
    According to the previous maintenance of the transmission experience and combined with the vehicle's fault phenomenon, the transmission must be disassembled maintenance. After the decomposition of the transmission, after careful inspection, in the mechanical and hydraulic components found the problem: ①N93 main oil pressure adjustment solenoid valve, N92 and N94 shift quality solenoid valve problems, resulting in the impact of the impact and shift impact The ② K1 clutch on the drum on the four positioning bracket damage, resulting in K1 the bottom of the friction film spline can not be engaged with the drum, resulting in the transmission brake into the forward gear transmission power after the transmission within a long time issued a similar friction sound. ③ visual observation by the visual torque converter appearance found that the torque converter has been exposed to a high temperature blue, for which we determine the torque converter lock clutch burn. ④ differential and the main reducer due to lack of gear oil lubrication, resulting in a larger transmission noise.
    In the replacement of damaged parts and in accordance with the standard work after the repair, the transmission equipment for a long time after the road test, other problems can be resolved, but the impact of 2-3 block problem still exists. And there is a phenomenon more special, the smaller the throttle opening 2-3 block shock stronger, if it is just 2-3 points in the pine when the throttle, the impact will be more intense, large throttle when the impact is not obvious. Since the 2-3 block shock and throttle opening has a direct relationship, and the transmission system pressure is increased with the throttle opening increases, so the basic can remove the internal mechanical components of the transmission problem, but also can exclude the hydraulic control valve Body and solenoid valve problems. Because the oil from the road analysis, 2 block when the N88 solenoid valve power off 1-3 block clutch K1 oil, N89 solenoid valve power to open the 2/4 block brake B2 oil, N90 solenoid valve power cut off the 3/4 clutch K3 oil circuit; 3 block N88 continue to power off K1 continue to engage, then N89 solenoid valve power cut off the B2 circuit, N90 solenoid valve power off K3 oil. 2-3 is nothing more than the switch between B2 and K3, the switch between the solenoid valve is between the N89 and N90 conversion, while the N92 solenoid valve also need to help maintain the shift point of the work pressure (Note: solenoid valve all For new parts), so the problem should be on the control signal.
    We do not see any problems with the automatic transmission, so we decided to shift the focus of the maintenance to the engine. For this reason, we observe the dynamic data of the engine control system. According to the analysis of the main data in the engine operating conditions, the air flow meter is slightly larger at idle time (the engine speed is 3.6 ~ 3.9g / s), then decided to replace the air flow meter. After replacing the air flow meter to continue the test, the fault did not change. Continue to observe the throttle opening, voltage signal and fuel injection pulse width signal, are normal, but for insurance purposes, we replaced a throttle and match, test failure still.
    At this point maintenance stalled. Is the control unit out of the question? As we all know, the public 01M, 01N have self-learning function, and the need for a long time to learn to finish the test. But this car has a long road test, failure did not rule out, but can only replace the control unit to try, but the results are still disappointing. At this point we are very confused, is it still a hydraulic problem? In this case, we have replaced the hydraulic control valve body, but also with the solenoid valve harness replaced, but the fault did not change the symptoms. It was so strange! Is the test time is not long enough? Day 2 we opened this car ran a long distance, come back after the problem still exists.
    At this point, maintenance personnel decided to this car "big throttle no problem, the smaller the throttle problem," the fault of the car for the mandatory study. After a period of time after repeated size throttle test, 2-3 block shock failure has finally been resolved.