I got a6d1 too... It's a pump that runs to heat at idle. Despite the code for a year, I can hear the pump working and heat works well. Don't worry about it, it's a hassle to get to by the drivers side front, near the intercooler hose but half way into the plastic partition.

Glue plug cel could be the gp or the gp controller. I have one that came up recently for 5, will do it when it gets warmer.