A Changan Mazda 32. 0L car with mileage of about 30 thousand km and equipped with 4 speed manual transmission. User reflection: the remote control used a day before the car is very good, second days in the morning using remote control unlock suddenly no reaction, lock the car has no reaction; the key inserted key Kong Kai / lock is normal, this is the first maintenance after the new car. Fault diagnosis: according to the fault phenomenon analysis possible reasons: (1) the remote control without electricity or damage; (2) the receiver is damaged; (3) the remote controller needs to be re matched because of the signal interference. The following steps are taken: 1) measuring the battery voltage of the remote controller is 2. 99V (standard value 3V). 2) the method of starting matching function to re match the remote control is: (1) opening the left front door; (2) opening / closing the ignition key after 3 times and keeping the closed position; (3) opening / closing the left front door 3 times, and then keeping the open position; (4) the lock actuators lock / open 1 times, indicating that the matching function has been started; 5 press the remote control of any key 2. Then, the door lock actuator was opened / closed 1 times, indicating that the remote control was successfully matched. The matching function of the vehicle is unable to start after the above operation. 3) the principle of remote control matching: key reminding switch signals to the instrument group, passing through the CAN bus to the PJB (dividing line box), PJB for the left front door lock switch and the key free module to provide the working power, and monitor the change of the voltage value (i.e. the signal). When PJB receives the key reminder switch signal and the door lock switch signal, the door lock will be opened / closed 1 times. At the same time, press the remote control to send the signal. After receiving the signal, the keyless control module generates a 2V voltage drop in the circuit supplied to the working voltage. After monitoring the voltage change, PJB controls the lock opening / closing 1 times, indicating that the remote controller has been successfully matched. If in the first start matching procedure, PJB does not monitor the voltage change value which will lock the remote control matching function, that is, no longer control the door lock actuator action. 4) the possible reasons that the matching function can not be started are: (1) the damage of the ignition reminder switch; (2) the damage of the left front door lock switch; (3) the PJB damage of the passenger side; (4) the failure of the key control module or the remote control; 5. The line fault between the door lock and the PJB between the key non key control module and the PJB. 5) check the ignition key reminder switch: the reminder switch is installed in the rear seat of the ignition switch, and its alarm sound can be used to judge whether it is good or bad. Open the left front door, the key is in the ignition lock core, there is "beep" alarm sound, pull out the key completely, the alarm sound stops. The check indicates that the reminder switch and the line are normal, because the alarm start and stop are controlled by PJB after receiving the switch signal. 6) inspection of the left front door lock switch: the door lock switch is located in the left front door lock, and the indoor light can be used to judge whether it is good or bad. Open / close the left front door, and the indoor light darkens from light. The check result shows that the door lock switch and the circuit are normal, because PJB receives the door lock switch signal and controls the interior lamp to light / extinguish. In addition, enter the data recorder, select the left front door lock switch (LFAJAR), check the status of the display by opening / closing the left front door, and judge whether it is good or bad. 7) check the keyless control module and remote control: the measuring module has normal working voltage, good tie up, and press the remote controller to change the terminal voltage of the measuring signal. Try to replace the remote control, the fault remains the same, which indicates that the key control module is damaged. After changing the key control module, the failure is eliminated. (3) attention to the fault diagnosis of this fault: (1) if there is a voltage change in the signal end of the non key control module, PJB damage is explained; 2. The damage of the remote control can not be detected and the spare parts can only be replaced. Failure comment: I guess the author of this article has undergone a good digestion after receiving the new model training of the host plant. Why do you say that? Because Changan Mazda 3 has just been listed, this vehicle is a new vehicle running 3000km, but the case is reasonable, and the conclusion is correct. Looking at the diagnostic steps designed by the author, I think the author has a deep understanding of the technology of repairing cars. Of course, some mechanic of a comprehensive model repair plant can also write a concise and comprehensive article. That is, they have a strong self-study ability. They have studied the raw materials of the original factory. They also accepted the training of the host factory. For electric control systems like central locking, there may be matching problems and possible hardware failures. They must be checked in accordance with the maintenance manual. The first step in this paper is to analyze the three reasons for the failure of the remote control before the start of the detection: one is the remote control or no electricity, the two is the receiver fault, and the three is that the previous matching data is lost due to interference. I hope other authors will start with the troubleshooting case and write out the troubleshooting case first, and take a moment of meditation to analyze the main or all causes of the failure. The second step is to measure the battery voltage of the remote control, because this is the most frequent fault, and it does not need to remove the parts from the car. It can not make a low error, that is to find the complex fault for a long time, and finally find the simple fault of the battery of the remote controller. The third step is to re match the remote control, but no match is successful. The fourth step is to analyze the principle of remote control matching. The fifth step is to analyze the reasons for unsuccessful matching. The sixth step is to detect the door lock switch. The seventh step is to check the control module and the remote controller, and draw the conclusion of the cause of the failure. This article is closely linked to one link, and the text is simple and clear. Without colloquial and complicated language, we save time for our reading.