If you are getting a P2102 error code associated with "Engine Fault, Workshop!" on the display, then there is most likely something wrong with the throttle valve.
The throttle valve and EGR valve can get gummed up or filled with engine oil causing them to fail:
Replacement of the throttle valve involves:
- disconnect battery negative terminal;
- remove top of cold air intake - three plastic clips hold the top half in place;
- remove cold air intake U pipe from top of assembly;
- remove cold air intake U pipe from bottom of airbox - two lugs on either side hold it in place;
- undo electrical connector to throttle valve and place safely out of the way;
- loosen hose clamp at bottom of throttle valve;
- undo and remove the bolt that holds the dipstick to the throttle valve;
- undo three bolts that hold throttle valve in place - there is one at the front and two towards the rear. Two bolts are short and the rear left bolt is long enough that it goes through the throttle valve and EGR valve. A short handle ratchet driver is essential. The bolts have a T25 torx head;
- tilt throttle valve towards radiator and remove rubber intake hose from bottom.
Installation is the reverse procedure.
If you're throttle valve has lots of oil deposits, then it may be worth removing the EGR valve and giving it a clean as well. Mine had lots of oil buildup in various stages of hardness.
Throttle valve and oil
Here are some pictures of my failing throttle valve. Lots of oil deposited inside:
Lots of liquid oil inside throttle valve mechanism:
I cleaned my throttle value of its oil deposits and liquid oil in the mechanism but it still generated an intermittent P2102 fault code. As a result, I had no choice but to replace it with a new item. My version was 03L 128 063 B. It has since been superseded with revisions C, D and E. The replacement from VW was 03L 128 063 E. The revision E part has a plastic butterfly flap. The B revision was metal.