Audi A4L sunroof won’t open problem & solution

An Audi A4L convertible was taken to garage just now. According to the driver, the sunroof of the car would not open from both the driver control and left rear door control. I tried to open it by holding the button in the down position, but only hear a click sound.
The first thing to do is to find out what the problem is. I applied a VCS vehicle communication scanner to the vehicle in order to retrieve trouble codes. According to the VCS vehicle, there was a faulty signal for sunroof switch. Then I decided to read J393 data stream.

I read the signal when the sunroof was in off position, and the result was front sunroof, front control panel switch 1111100.
When I pressed the sunroof switch, the sunroof turned up, and the signal read: front sunroof, front control panel switch 1111110.
When I pulled the sunroof switch to turn down, the signal was: front sunroof, front control panel switch 1111101.
When I turned on or off the sunroof, the auto diagnostic tool would showed signal input. But there was no signal when the widow was rotating. I suspected that the problem could be with the sunroof switch, so I disconnected the switch and read the data stream again, and the result was still 1111100. Well, I was wrong. The problem was probably not with the switch.
Then I check the circuit from switch E139 to J254 sliding sun roof control unit, which latterly turned out alright.
As the circuit was alright, I suspected that the problem could be that the sun roof control unit could not recognize the switch signal. Since the sunroof motor was with the control unit, I first replaced the motor with a new one, and then tried to open the sun roof again. The sun roof can be successfully opened this time.