My 2006 XK8 convertible keeps showing a second-order (yellow light in speedo) error message -- "Check rear lights. Cruise not available". This happens within the first few miles of driving. When I check the rear lights, only the license plate lights are out. If I stop the car and turn off the motor, the error clears, but it always comes back after a few miles. Has anyone else seen this?

 

Check the brake switch. There are MANY posts, very common problem.

 

Search the XK8/XKR forum section using "brake pedal switch assembly replacement" as your search phrase. There are multiple schools of thought on how to go about making this repair....

 

yep +1

 

Unfortunately, I can't make my car throw the error or douse the license lights by any combination of brake application and turn signals. It happens when the car is darn good and ready.

 

Jim, The brake pedal "switch" actually has 2 switches; one normally open and one normally closed. Doesn't look like something that would ever go south on you, but age will cause failure, guaranteed. Bite the bullet and get a replacement now, while you're just getting warnings of impending failure. There is at least one forum member who will overhaul yours very quickly and inexpensively, but if your car is a daily driver, you'll be down for the turnaround time. I bought and installed a used one off of eBay, then had my original overhauled and it is now bagged and ready for if/when the replacement unit starts acting up (nope, sorry, not for sale....).

Replacing the switch is a two or one person job, depending on whether you remove the whole bracket from under-the-hood, (tight-quarters, two-person kind of thing), or simply crawl up under the dash (taking the driver's seat out of the car helps immensely), and loosen the bracket nuts/bolts holding the switch to then swap it out by yourself. I am a slender 5' 9" and was able to swap out the switch without removing the bracket (or the front seat), but for the first time in my life, was happy that my hands aren't big enough to palm a basketball. It's still tight quarters and a lesson in patience, but faster than removing the bracket from the firewall. Wear long sleeves; the floor carpet is surprisingly abrasive.

Search for "brake switch replacement" threads in this forum, which will help educate you make the changeout so much easier.

 

FWIW, these brake switches rarely fail outright. They seem to have long periods where they work, and then they fail for a bit. Then work again. A meter test is basically useless.

Separately, my understanding is that the rear lights are part of a "monitored" circuit. It means the control module always sends a small current through the lights and can detect if any of the bulbs are out (like a home alarm system). For all I know, the license plate lights are also monitored. You might want to just change them outright, and "while you are there" check for corrosion or any sign of damage. The earlier cars had undersized ground wires on the light clusters that ended up overheating and causing issues. The fix was to add wiring to help with the extra current. License plate is on the trunk lid, so trace the wiring off of that too for anything unusual. I suppose you could take a bulb out and test that the message comes up on the dash "on demand" to confirm the theory.

Best of luck, keep us posted.

 

^^ 2001 up licence plate (and rear sidemarker on US cars) lamps appear to be monitored, so you should get a message if any of these are out.

Agree that brake switch is favourite for intermittent light/cruise message, though