Been a while since I've had a forum presence , here's my issue of the day.
my late '94 xj6 (706184) bulb fail indicator always on with parking & headlights. As I do a walk-around, all external lights are lit, although I've had occasional side marker lights with intermittent socket contact. Are any other lights associated with the bulb fail module? Or maybe itself may be the problem. Not a big deal on the overall scheme of things, but killing that dash indicator would be nice.
thanks for any ideas-

 

Check the bulbs in the tailgate/licence plate lights. Fogs too if you have them.

 

Check them in the dark with ignition on and brakes applied.
As Lawrence says it could be just a licence plate or similar and it is easier to pick up the problem in the dark.
I sold my XJ40 but still run an X300 and went through a similar problem with one tail lightbulb I could not pick until nighttime.