2000 Golf GLS TDI Auto Stuck in 2nd or 3rd Gear

I have a 2000 Golf GLS TDI, automatic transmission seems to be stuck in either 2nd or 3rd Gear. It has very weak pick up starting from 0, and almost redline at about 70 mph. Can someone please tell me what could be wrong with my car? Thanks in advance.

Your car is probably in limp mode. Could be due to a number of things. What you need to do is locate someone with VagCom and scan for codes. If you shut down the engine and restart it, it MAY reset to normal, but it may not.