When encountering a car故障 code CDA54F, there are several steps you can take to solve the problem. First, check the power supply and ground connection of the control unit, and make sure the communication line is connected properly. If the control unit is not working correctly, try programming it again. If that doesn't work, you may need to update the control unit. However, before doing so, it's important to check the communication line connection first. 

To do this, you can follow the following steps: 

1. Check the power supply and ground connection of the control unit. This is the most common cause of a car故障 code. 

2. Check the communication line connection. Make sure the line is not broken or disconnected. 

3. If the control unit is not working correctly, try programming it again. This can be done using a diagnostic tool or by connecting the control unit to a computer. 

4. If programming the control unit doesn't work, you may need to update it. However, before doing so, it's important to check the communication line connection first. 

5. If you are still having trouble, you may need to consult a professional mechanic or bring your car to a repair shop.