1.6 hdi pipe

[aalpha_taxis]

I have a c5 06 reg 1.6 hdi. The em light came on continuously and initiated limp mode (no turbo). Upon closer inspection I noticed a small pipe hanging loose in engine bay. I was wondering if anyone could shed light on to what it is, and what it does. It's a small rubber ended pipe containing a clear plastic tube, it runs under the oil filter. I reattached the loose end to a nipple on the side of the turbo base. This ended limp mode and turned off EM light. Just wondered if I had put it in the right place, and what it's purpose is.

[wheeler]

Posting a picture would be the best way for somone to identify the pipe.