Totally unrelated to Alfa electronics, but my daily use car is a 2005 Ford C-Max. It has no bulb failure warning system and no can bus control to lighting system. I had an appropriate non-canbus HID system which happened to fit the front fog lights, so I fitted it. Worked fine. Then I started to get in related ecu errors, ABS system failure, electronic parking brake failure VCD failure etc. they'd come and go randomly. Then noticed it only happened over the late Autumn/Winter fog season. I swapped the HID kit for a proper canbus set if ballasts on the same bulbs, and all the odd errors went away. No idea how or why!
Just thought I'd share as sometimes, circuits that shouldn't be in any way connected seem to share a common connection somewhere and the unprotected power spikes that the slimline/ non canbus ballast HIDs produce could be a possible cause, however unconnected they may appear.