I installed LED reversing bulbs and LED indicator bulbs to my 2006 A6 3.0 TDI S-Line Quattro saloon. Don't have any issues with the rear bulbs (no can-bus errors) but I do get a can-bus error on the fronts. If I switch on the hazards or indicators for about 4 seconds the error goes away and doesn't appear again unless I remove the key from the ignition for more than 5 minutes. I plan to fit a 25W load resistor across these when I upgrade the front headlights to HID type. Another issue (depending on your perspective) is that ever 20 seconds or so you get a single flicker from each lamp in sequence when the car performs a can-bus scan. Looking on the forum one member has recommended that installing a small capacitor (about 20v, 63uF) across each bulb will stop this, just waiting for a reply to confirm and will give it a try. It takes less than 5 minutes to remove the rear light units so will test the theory on these first.
P.S. I bought the LED bulbs on ebay and they are suppose to be suitable for can-bus cars.
Thanks Brian, I am having a bit of a problem with mine...when I installed the left hand side indicator it worked fine without any canbus error. I then fitted the right hand side and that when things got weird...the right hand side did not give a canbus error either but only worked for 4 flashes then stopped. Would not work again until I took the bulb out and put it back in and again the same problem...four flashes then nothing..doing my noggin in!