Just got a 2007 TDV8 with a "Check Rear Fog light" message on dash, and rhs rear tail/fog not lit. Indicator, upper tail light, brake light working fine.

As only one side assumed simple bulb replacement, but have checked bulb and it is definitely fine.
Connectors look clean, wiring to lamp unit looks ok. All completely standard, ie no LED conversion or any other lighting upgrades.

Any ideas what else could cause this? Presumably these aren't individually earthed?