I have a 2008XKR and have installed a 2012 body conversion kit changed all lights to LED and now I keep getting a warning on the instrument cluster panel showing that brake lights and signal lights are not working but everything is working perfectly fine Any suggestions

 

Your LEDs have different electrical characteristics than the original lights, so the car thinks they are malfunctioning. Probably need to add resistors to make the load look right.
I followed George Kale’s instructions when I changed my tail lights to LED, you’ll need a similar strategy for other lights converted to LED.
See post #66 in this thread:
Tail light upgrade