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There are 2013 BMW 328Li cars with mileage of about 10 thousand km. The car failed to start because the remote control failed and was towed back to the repair shop for repair. After taking the car: first, verify the failure of the user, because the mechanical key has been used to unlock the vehicle, the vehicle is interlocked with the remote control, and the control lock of the vehicle does not respond. Press the start button and all kinds of signal lights in the meter are not lighted, that is to say, the KL.15 bus terminal is not activated. The boot machine does not work, of course. Press the start button continuously. There is a text message in the meter. "There is no remote control in the car!" At this point, the two remote controls of the vehicle are all carried. A remote control is placed on the emergency boot of the vehicle's right side of the steering column. Press the start button, the instrument still displays the text message of "no remote control in the car", and the KL.15 is still unable to activate. Because the KL.15 bus end of the vehicle is not activated, it is impossible to detect the ISID through the diagnosis. Only through the analysis of control principle to find fault points. A new module, the front electronic module FEM, is introduced into the vehicle, and FEM is the central control module in the vehicular network. FEM ensures the functions of the following control modules: the function of the foot space module (FRM), the convenient entry and starting system (CAS), the connection box electronic device (JBE) and the central gateway module (ZGM), the entire boarding control function of the former CAS control module is fully integrated in the FEM, and the mechanical boarding square is only limited to the opening of the driver's door lock. Key jacks are no longer used in this car. As a standard function, you can start the vehicle without a key. This function is called "passive start". But identification launchers still need to be enabled when boarding. FEM is the main control module of the central control lock and the key free convenient boarding and starting system. All the functions used to control the key free convenient boarding and starting system are integrated in the front body electronic module. This car does not have the configuration of the car without key. The remote control can unlock and interlock through the wireless signal or lock the vehicle from the center. The remote control receiver has a transmitter receiver module, which can establish communication between the identification sensor and the remote control receiver. The wireless signal of the remote controller is demodulated, processed and detected in the remote receiver. That is to say, there is a constant value belonging to the vehicle in the wireless signal of the remote controller, which is checked by the remote receiver. Information is transmitted to FEM only when the value is correct. Then the radio signal is identified in the FEM. If it is an authorized request, the front body electronic module makes the vehicle unlocked or locked when pressing the start button, the start button will pass the signal to the FEM through the wire, and the FEM activates the internal antenna to find the remote control. If the remote controller is within the specified range, it is activated, and then sends out high frequency wireless signals, and then the authentication and recognition process facing the wireless signal is the same as the verification and identification process of the remote control directly unlocking or locking. There is an emergency starting position on the right side of the steering column of the vehicle, where there is a loop antenna. The loop antenna is connected with the front electronic module (FEM) through a 2 core plug. The loop antenna is used for communication between the signal transceiver chip (in the remote controller) and FEM. In case of unfavorable conditions, the identification sensor inside the carriage can not be found. In this case, FEM outputs a check control information in the instrument cluster. According to the corresponding information, the remote control must be placed on the right side of the steering column. The signal of the remote control in this position can be communicated directly through a loop coil and FEM without a remote receiver. After the successful identification, the FEM is allowed to start. Combined with the failure analysis, the control modules involved in the control are the remote control, the remote control receiver and the FEM. The control modules of the control are the remote control, the inside of the vehicle and the FEM, and the control module of the control during the emergency start of the vehicle is the remote control and the loop coil. The three mode of control is only remote control and FEM. It seems that the fault points are in the two parts. The two remote controllers have the same fault, and the probability of two simultaneous damage is not very high, so the fault points are locked on the FEM. In order to determine the results of the analysis, in the case of disconnecting the vehicle instrument, the FME and DME vehicles are immediately unlocked or locked and started at the same time. The key to this key module (ZGM, KOMBI, DME, CAS) is not recommended. It is easy to cause data exchange confusion among vehicle modules, such as the chaos of the vehicle mileage, resulting in the incapable of changing the results. So before disconnecting, the instrument connection of the vehicle was disconnected, and CAS and ZGM were integrated in FEM. Finally, the new FEM is ordered and programmed, and the vehicle trouble is eliminated.