I have a 1997 XK8, with "rear bulb failure" i had previously added the additional ground and eliminated the problem. It is now back with a new wrinkle.
When you press the brake pedal the rear bulb failure indicates on the dash and all of the rear lights go out. If i reach in on the passenger side and press against the connector going to the passenger bulb housing all of the rear lights will come back on. Whamo press the brake and all go back out.
I am leaning toward a weak LCM and having the relays let go under the brake light load.
I will be cleaning and checking connections later today.
Any suggestions anyone?

 

I would first check the ground that is in the trunk at BT2 location page 18.

Link http://www.jagrepair.com/images/Auto.../jagxk1997.pdf

 

' . . . press the brake pedal . . .' may be a clue.

A failing/failed brake switch causes all sorts of erratic behavior.

It is 12 degrees in North Georgia at the moment, about 30 degrees below normal. How is the weather in Ketchikan?

 

Thanks for the quick info Gus. I will look into it this evening and get back with the results.

Testpoint, it's 43 and raining in Ketchikan. I am currently visiting wife in Omaha at -11. Be glad to get back to Alaska where its warm.

The XK8 is her cat mine is and XJ8 back at home.

 

Good morning Gus, I checked, cleaned and tightened ground connectors and no change. I am going to use contact cleaner and and recheck the plugs. i have noticed that if the headlights are off the turn signals work until i press the brakes and then the rear turn signals shut off. they come back on after releasing the brake pedal.

 

Sounds like a failing brake pedal switch to me. Had to change it in my wife's 2006 XK8 in October 2012 due to the "cruise not available / check rear lights" messages being displayed on the dash. As expected, a new switch solved the problem....

 

Can you check the voltage at the light and and have someone apply the brake as you outlined and see what you get. I am not discarding the possibility of the brake switch just another check.

 

I wanted to let everyone know I got the rear bulb failure resolved. while i had the connectors to the rear lights disconnected for cleaning with contact cleaner i found that the passenger side ground connector showed signs of arcing to the spade tab on the light housing. i looked at the connector and found that the tabs were spread open and appeared to make poor contact.
i pried the ends of the connector closed, cleaned with contact cleaner and coated with copper coat never-sieze. all lights are working normal. I am sure glad to have dodged the brake light switch bullet, those babies are expensive.

Thanks for all your help Gus.