Join Date: May 2016
Car: 2004 Contemporary SE CDTi
If you still have the issue with the warning light, I've had a couple of issues, which I solved which may help you:
1). Remove the rear light bulb holder unit, reove all the bulbs and clean the contact points of the holder with a fibreglass pen, this will remove any surface corrosion which may be giving a high resistance (had this issue a few times).
2). separate the rear light wiring loom plug, again, clean the prongs on the plug and spray with a switch cleaner (it took me ages to solve this problem the first time it happened!)
Hope this helps,