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Mercedes Benz S350 M112 engine, 722.6 transmission, 220 chassis Mercedes Benz S350 car. User reflection: the vehicle is unable to start a fault. This is the case: the customer goes to the car in the morning, can not unlock the vehicle with the remote control key, and has to use the mechanical key to open the driver's side door. At this time, the ATA burglar alarm is called, and the key is inserted into the ignition switch EIS after entering the car. The alarm is automatically lifted and the vehicle is started at that time. After the current line is about 1 km, it will not start again after parking. That is, the key can be turned on, the indicator lights are all bright, but when the EIS is in the starting gear, the starter does not work. Fault diagnosis: connect the DAS diagnostic instrument to test the vehicle quickly. The result shows that the electronic ignition switch control module EIS can not communicate with each other. In addition, it is found that the left front body control module, the right front body control module, the rear body control module, the PSE, the door control module, the seat control module, the air conditioning control module and so on, can not communicate with the "control module" column. But the control function of the above parts is normal. Initial quick test list. For the 220 vehicle, the EIS control module is the communication point between the CAN, the engine control module and the transmission control module. Because the current EIS control module and many body electric control modules can not communicate the fault, it is decided first to check the hand from the ignition switch line, and to repair the fault of the car. Normally, the EIS control module can connect with the DAS diagnostic instrument without the insertion of the ignition key. There is no exception for each conductor of the EIS control module alone. At this time, it is very doubtful about the failure phenomenon, why the DAS diagnostic instrument can not communicate with the control module of the left front body control module, the right front body control module, the rear body control module, the PSE, the door control module, the seat control module, the air conditioning control module and so on, and the above parts can work normally. It is possible to deduce that the current EIS control module "15" and "15R" circuits should be output normally from the status quo that the above components can work normally. Why does the "50" circuit fail to output? The EIS control module has a infrared receiver and remote controller in the key socket, which can exchange data with the remote control key. When the ignition key is located at position 2, the "15" and "15R" circuits are connected, at this time the engine control module is powered, the encrypted data will be exchanged between the ME control module N3/10 and the EIS control module N73, and the driving approval code is calculated, and then the calculation results in the ME control module N3/10 are compared. If the validation is successful, the start approval is issued. On the other hand, the vehicle is not allowed to start. At present, it is possible to assume the CAN communication function in the EIS control module, which leads to the failure of many body control modules to communicate properly, and can also cause no data exchange between the N3/10 control module and the ME control module, resulting in the failure of the vehicle to start. At present, the function of "unlocking" and "locking" of the remote control key to the vehicle can be used normally, indicating that EIS has normal function of radio signal processing. Contact the owner to take KG card for the test, found that the vehicle can be started smoothly, at this time the rapid test of the vehicle, and the same test results before (the related body control module is still unable to communicate). The function order of starting the engine using the KG card is to press the KG start / stop button S2/3 on the shift lever ESM, send the wake-up signal to the remote control key A8/1 to the remote control key A8/1 to send its approved code to the HF antenna, the roof control board control module N70, the KG control module N69/5 to EIS control module, and evaluate its compatibility. If the check is correct, the circuit 15R is connected to circuit 15, and the engine is allowed to start. In summary, it can be concluded that the failure of communication between the EIS and the engine control module is the cause of the failure to start the vehicle with the ignition key. Fault summary: in the process of vehicle testing, we found several problems to share with you, hoping to be helpful for future maintenance. (1) after the ignition key is inserted into the EIS, the infrared communication between the ignition key and the EIS control module is carried out. The remote control key code is identified by the EIS control module. If the key is valid, the rotation lock within the EIS control module will be started, while the "15C" circuit is connected, and the remote key A8/1 is allowed to turn the "1" and "2" circuit "15R" and "15". When the "15" circuit is connected, the engine control module is powered, the encrypted data will be exchanged between the engine control module N3/10 and the EIS control module, and the driving approval code is calculated, and then the calculation results in the engine control module are compared. If the validation is successful, the "start recognition" signal is issued. On the other hand, the vehicle is not allowed to start. 2. Remove the A switch of the ignition switch, and the ignition switch can still operate. The phenomenon is not different from before. The KG card can still start the car. 3. Remove the ignition switch's B plug 7 and 8 CAN line connection end, the key can operate, the instrument light is bright, but cannot use the KG card to start the vehicle. The remote-control door lock function is normal. 4. Remove the ignition switch B, insert 3 and 4 CAN line connection ends, all functions fail, only the key can be turned, and the meter has no indication. The remote-control door lock function can not be used. 5. When the B plug pin 1 has no power, the ignition switch is unable to operate. At CGW, when all the EIS plugs are removed, the DAS diagnostic instrument can still communicate with the previous control module that can establish communication (see the initial detection list).