2005 XK-8. When I turn on the headlights I get a “ check rear lights” warning and the yellow light. We checked the rear lights, the wiring, etc. I took it to a local guy who does electrical issues on expensive and/or collector cars. He thinks it’s the circuit board in the back. He said they aren’t available to order anymore. Anyone have this issue? And does anyone know how to fix it? Many thanks! I’m so tired of looking at the yellow light when my headlights are on.

 

Did you check the license plate lights and the side lights? A bad bulb can trigger the error.

 

Though it's not necessarily or likely your problem, I've bought and burnt out most of the world's inventory of Lamp Control Modules for '97 XK8s on eBay. There may be a few left however...I thought Jaguar got rid of the modules on later models, but if not, you too could probably find one on eBay.

 

A slightly mismatched bulb can cause this, or the brake switch on the brake pedal under the dash - this will often accompany a cruise control issue as well.

 

Wattage of bulb can matter because of the way the module does the detection. Make sure all combinations work, rear lights and brake lights, the bulbs are a double filament type.

And you are not trying to use LED bulbs are you? That can be done but brings a whole other level of difficulty to make the message go away.