First, no need to use all caps here nurface, we're all civilized these days. To help you on your troubleshooting, I have gone thru a period where the 'check rear lights' came on in my car when putting in LEDs.

When does it come on? when you turn on your lights? only when you brake? Most likely, you just shorted out a brake or tail lamp bulb with all that bass. lol. Seriously, just use a friend and see which one is out. One important note, you cannot replace these bulbs in the jag with regular ol 1156 or 1157 bulbs from the auto parts store. They are of different resistance and will keep giving you messages on your dashboard, even though they are working correctly. If none appear to be burnt out, either in parking mode or under brake pedal, and you are not sure, check each of your brake/tail lamp bulbs to see that they are P21W. report back when you have diagnosed a little further.

 

or the battery is just a little low.. which gives you false brake light failures..

 

genius, can it also give a false light if the car is running?