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A motor vehicle with a mileage of about 50 thousand km and a E71 sports car with a N55 engine in 2011 is a sports utility vehicle of 2011 X6. User response: the key entry function of the vehicle is invalid. Inspection and analysis: the maintenance personnel test the car. First use the remote control to lock all the doors, and then pull the door handle, the door can not open; unlocked with the remote control, and then touch the door handle induction zone with the hand, the door is not locked. But the keyless starting is normal, and the meter and vehicle information display is not abnormal. This shows that the work of the anti-theft control unit is basically normal. Detect the burglar control unit and find fault code A103---- CAS EWS bus failure. The door handle control unit is connected with the burglar control unit through the EWS bus. If the bus fails, the function of the door handle will naturally be affected. First remove the handle on the outside side of the driver's door and disconnect the connector of the handle control unit. According to the circuit diagram, the pin number 1 of the connector is bus signal line, and the voltage of this line is measured to be 0.2 V. The voltage of the substation should be close to the battery voltage under normal condition, so there should be a problem with this line. Next, measure the resistance of the bus to the grounding iron, the resistance is 60 ohms, normal. The resistance of the end pin to the corresponding end pin of the anti-theft control unit is measured, the resistance value is 0.8 ohms, indicating that the circuit is turned on normally. Up to now, you can make a judgement that there should be a problem with the bus driver of a door handle control unit. Remove the handle of the other door one by one and disconnect the connector of the control unit separately. When the front door passenger door is broken, the signal voltage of the bus is restored to normal, indicating that the fault is here. Troubleshooting: replace front passenger side door handle assembly, troubleshooting trial run.