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The mileage is about 14 thousand km, the model is F02, and the BMW 740Li car is equipped with N54 engine in 2012. User response: when a vehicle bumps or bumps to the side, it will automatically jump to neutral. And the engine fault lights are temporarily lit up before the gear is stopped, and then the vehicle can move forward. Fault diagnosis: after connecting ISID, connect ISID for diagnostic test, read fault content as follows: D02D58 a signal (motor 1 wheel torque, 41.3.4) invalid, DME/DDE emitter; D01557 one information (motor 1 wheel torque, 41.3.4) missing, receiver ICM, transmitter DME/DDE; D01558 one information (motor 2 wheel torque, 4) 1.3.4) missing, receiver ICM, transmitter DME/DDE; D0156D one information (motor 3 wheel torque, 61.3.4) missing, receiver ICM, transmitter DME/DDE; D01570 one information (motor 4 wheel torque, 40.3.4) missing, receiver ICM, transmitter DME/DDE; DOlB3F 1 information (motor 5 wheel torque, connection) missing, connection Receiver ICM, transmitter DME/DDE; DOl AO8 one information (motor 6 wheel torque, 61.3.4) missing, receiver ICM, transmitter DME/DDE; D01646 one information (acceleration pedal rod angle, 40.1.4) missing, receiver ICM, transmitter DME/DDE; D018E1 1 information (crankshaft 1 torque, rejection) missing, receiver transceiver, launch DME/DDE; D76FO2 signal (wheel standard torque, 40.3.4) invalid, DME/DDE transmitter. Delete the fault storage for the road test, the process of testing, when a section of the deceleration belt, the engine fault lights suddenly light, then the engine speed suddenly rise very high, the block jump to the air. Connect the ISID again for diagnostic testing, and read the fault contents consistent with the above. Implementation of the detection plan, the above fault content is divided into two major categories: information loss and CAN/F1exRay bus system analysis, interface fault information "signal ineffective". When the receiving control unit does not receive the information sent by the transmission control unit, the receiving control unit records the "information loss" fault, and this kind of fault is mainly caused by the interference of the physical connection between the participating control units. A possible cause: bus wire grounding wire bus wire to power supply voltage short circuit bus wire circuit breakage circuit breaker (wire breaking) fault, corrosion, dirty contact joint control unit fault (such as plug connection damage) (a few cases) added incorrect (bus connection) calculation information The most probable cause of failure is missing. The detection step will limit the fault within the defined range by probabilistic analysis of fault records (probability calculation). The detection plan is as follows: the missing information of the transmitter is 1. DME----***----8 16, starting from the most likely control unit area to locate the fault. If necessary, continue to locate faults in the second high possible control area. The possibility of failure is corresponding to the number of asterisk displayed (*). * * * * *: high probability; *: low probability, and in brackets display the stored faults and the maximum possible number of failures. At this time, for example, (5/46), there are 46 possible faults for the corresponding control units, 5 of which are stored. In most cases, a number of information malfunction control units do not list all possible failures because the information failure is connected to the corresponding vehicle functions. For different control units, different vehicle types and different special equipment, the maximum possible number of failures varies. When there is little information failure in the corresponding control unit, the value expressed in parentheses is of special significance (for example, (2/2)). If the failure share of another control unit is summarized as, for example, (23/65), the preceding control unit area should be focused on finding the fault. Special circumstances: it is conceivable that, in special cases, a reception control unit may record information failures of different radio stations, although the receiving control unit itself will not appear in the (fault) profile because other control units do not need the signal ammonia for the receiving control single element, for example, if there is an overview. Control units with low probability of occurrence of multiple faults should check additional fault data. If the location is always referred to as the same receiver, a fault inquiry is continued within the control unit. Tip: systematic analysis of missing information involves occasional failures. If there is a continuous system failure, the fault should be identified when the vehicle is tested. The fault storage is associated with the DME, and the detection plan analysis also believes that the possibility of DME's failure is higher than other control units. Then the power supply, grounding and terminal connection of the DME are checked, and the results are normal, so the analysis considers that there is a fault inside the DME. When the vehicle runs on the bumpy road or the direction of the direction, the DME can not transmit the torque output information to the bus normally. The transmission control unit automatically jumps to the blank immediately after the information is not obtained. Replacement of DME control unit, programming and code for vehicles, repeated road test, failure phenomenon did not appear again, troubleshooting.