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bmw 528i speedometer not working
After a fault occurs, if the engine is stopped and restarted after a while, the fault will disappear immediately, but the problem will reappear after a period of operation. It seems that we can't always look around the automatic transmission, we should consider the engine control system.
The fuel pressure gauge was connected for a road test. As a result, when the transmission failed, to be precise, the engine power should have a problem, the fuel pressure changed significantly. In order to work cautiously, wait for the road test again in the evening or in the morning. As a result, there is basically no obvious change in fuel pressure, and the car runs well. In this way, the fuel pump was replaced and the test run was repeated (due to the continuous high temperature in recent days), and the fault did not appear again, and the fault was completely eliminated. Summary: The failure of this car is rare, but we have gained a lot of inspiration from the maintenance process: the gear shift control and other control functions of the transmission can no longer simply use the information of the throttle valve and the information of the air intake to reflect the load information of the engine; More and more problems show that the relationship between the engine and the automatic transmission is getting closer; the load information of the engine is reflected in the overall operating conditions of the engine; the control range is getting wider and wider. Due to network control reasons, it is necessary to comprehensively consider the performance of the whole vehicle, which is not only reflected in the engine operating conditions, ABS, and electronic power steering.
As far as the failure of the car is concerned, the power performance of the engine is reduced due to the air temperature, which in turn leads to the imbalance of the shift control of the automatic transmission and weak acceleration. In fact, this kind of control is also a matter of course. The transmission ratio is different and the output torque is poor. The transmission electronic control system will naturally perform the function of delaying shifting. Interrupt the lock-up control function of the torque converter (the load and vehicle speed can be realized by the lock-up control, but once there is a problem with the real load of the engine, in order to meet the change relationship between the output torque and the transmission ratio, only the hydraulic connection control can be realized), so that the transmission's The rapid increase in operating temperature gave the maintenance personnel an illusion that it was ultimately a control issue.
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