Good day all,

I have a 2010 Jaguar XJL and I can’t get a Massachusetts inspection sticker because all exterior lights are required to be working properly. The issue is with one of the rear tail lights: the running light does not come on when the headlights are turned on, but the same light does work when the brakes are applied.
So far I have:

• Traced the wiring
• Replaced the light assembly
• Checked the obvious connections

I still can’t seem to figure this one out. Has anyone run into this issue before or have any ideas on what I should check next?
Thanks in advance!

 

Probably need to get the car on a SDD system and check for errors. The lights are operated by a module providing a ground. It's kind of backwards from what you expect. The lights have 12 VDC all the time. The only come on when the module provides a ground after you move a switch. As you found out this has nothing to do with the lights themselves if the module does NOT provide a ground when commanded to do so. My guess is it's a module failure of some kind.

One suggestion for just in case? Try swapping the R and L lights to see if anything changes. I bet it won't but it worth the small amount of effort to check.
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