The TOYOTA crown new car, which runs about 1200km, is reflected by the owner: after the vehicle is equipped with a navigation system, it is found that the air conditioning system works abnormally. The symptoms are that the wind mode in the front and the mist out of the wind can only be used, and the other modes are invalid. Troubleshooting: the primary reason for the fault is to install the navigation system to cause the interference of the control circuit of the valve servo motor, so the navigation system is dismantled first, and the result of the failure is still the result. Check the condition of the car and operate the air conditioning control panel to confirm that each function key is good, but in the process of repeated operation, it is found that every time the ignition switch is opened, the front demogging indicator flashes, and the maintenance manual is consulted. It is found that the air control module will activate the valve servo when reconnecting the battery and opening the ignition switch. Motivation, initialization. The front fog indicator lights flicker for a few seconds, indicating that the initialization is complete. Therefore, it is very likely that the power supply line of the air conditioning control module is defective. Check the fuse and air conditioning control module's power cord and ground wire, normal. It is doubted that there is a problem in the air conditioning control module. Instead of the test, the fault remains the same, which eliminates the failure factors of the air conditioning control module. Use the diagnostic instrument to diagnose the air conditioning system without fault code. Start the air conditioning system to read the data flow related to the air door, the front air door position data is 9~17, the two-way ventilation valve position data is 32~38, the foot valve position data is 45~70, the foot / mist damper valve position data is 84. Comparing these data with the maintenance manual, it is confirmed that within the standard value range, it is possible to determine the control part of the air-conditioning system. When checking the throttle actuator, it is found that the foot throttle servomotor is not properly installed during initialization. Re install, then test the car, the symptoms disappear completely, the maintenance work is over. The new style crown valve servo motor is different from the early model. As the air conditioning system is equipped with a local bus, the air conditioning control module can use three wires to control four valve servomotors, one of which is a bus, the reference voltage of the bus is 5V, and the signal is square wave pulse signal. Therefore, the four throttle servomotors are connected in series and can realize network communication. The throttle actuator is composed of the valve servo motor and the intelligent connector. The intelligent connector is actually a IC module. It receives the square wave pulse signal of the air conditioning control module, then drives the valve servo motor, and sends the feedback signal back to the air conditioning control module. The failure of this example is due to the incorrect installation of the foot valve servo motor and the incorrect feedback signal received by the air conditioning control module. Therefore, the initialization setting should be carried out each time the ignition switch is opened. The failure of the initialization setting will disable the related wind mode and activate the front demogging instructions in order to remind the driver. Repair as soon as possible.