A Buick Excelle with a mileage of about 11 thousand km. After the user has been decorating the vehicle, there is a failure of the central control door lock, that is, the remote control and manual switch can not lock the door. Troubleshooting: (1) checking the power supply and the iron lap of the lock are normal. When the input signal is not working, the bypass is broken, the voltage of the power supply is broken, and the bypass is connected to the iron. When the blocking signal is not working, it will open the circuit of the switch, break the supply voltage, and turn on the tie when working. In this case, the door lock switch and the line are judged to be normal. 2. Check the left front door lock and anti-theft switch. The result shows that the switch and the circuit are normal. After the replacement of the new central control module, the fault is still detected. After the replacement of the new remote control module, the failure is still. (4) test the door lock output control circuit and each actuator by direct power supply method, that is, connect the 2 foot of the central control module plug with the battery power supply, and then tie the No. 3 foot to the normal: the 3 foot is connected to the power, the No. 2 foot tie iron, and the lock is unlocked normally, which indicates that the output circuit and the lock actuator are normal. The systems are tested separately. In repeated tests, it was found that the relay in the central control module had "popping" action, but the module could not output the control voltage. Another strange phenomenon is that the locking signal line is unlocked when the lock is unlocked, and the interlocking signal line is also cast iron; when the lock is locked, the two signal line is unlocked and locked simultaneously. The resistance of the two signal line is directly measured, and the two signal line is short circuited. Then, the door lock switches on the two signal lines are disconnected in turn, and two lines of the left front door lock, the anti-theft switch and the remote control module are still short circuited. The next point is that there are only two wiring points, and when the wire harness is disassembled, it is found that the actual dividing point is more than two of the lines on the circuit diagram, and these two lines are not shown on the circuit diagram. (5) apart from the entire wiring harness, it is found that more than two wires lead to the 205 plug, and the other end of the plug is not connected, which is two suspended lines. In the process of film placement, the water of the film has entered the 205 plug, causing the two plug-ins to be rusty and short circuited, thus causing the entire central control door lock to be unable to work. After the derusting treatment, the central control door lock works normally.