The turbo actuator controls a valve inside the turbo. This actuator is a precise motor connected to the valve through a series of metal links/joints.
First image is the actuator as seen from top of engine. On my engine it is located front left of the engine.
Second image is the actuator from the bottom, the linkage can be seen there as a 90 degrees metal linkage.
In DIS I got this error.
4CD0 DDE : Charge-air pressure actuator
This error is a combination of 3 possible errors.
1 : Electrical fault
2 : Mechanical fault
3 : Overtemperature
In my case, I could hear and feel the actuator "humming" when the car was unlocked. At this point the actuator will reset it self, so I figured that the electrical part was not the problem.
I then tried to move the actuator up/down by hand. And found that it moved very rough, and sometimes not at all.
This led me to believe that the problem was mechanical, so I lubricated the linkage joints with sewing machine oil..
After a few manual movements, the actuator moved freely over the entire range again.
No error seen since :)
Job done !