Hi all, apologies as I've scoured the pages for solution yet to no avail. One person had this listed, but no one answered their inquiry.

I have a "brake assist failure" lamp illuminated on my 2006 S-Type, base, 3.0 at 123k. All is well with her otherwise. Last owner (father-in-law) advised
lamp illuminated after putting in a new vehicle battery. The fluid is topped, and brakes strong and reactive.
Any guidance is appreciated.

 

Do nothing until you ensure that the battery is FULLY charged. You would be amazed to find how many different issues are caused by low battery voltage. Owners often waste a great deal of time, money and effort trying to find the cause of random symptoms when the cause is simply a lack of proper battery voltage to the multiple modules in modern cars, Jaguars included. New batteries are almost never fully charged at installation!

 

Hi and thanks,
Okay, I'll put the charger on it this morning. I'd driven 11 hours or so from Boston..but, right, could be it's not charging fully.
Will update. I wondered about brake fluid reservoir caps and all matter of other potential gremlins.
Appreciated!

 

did you find the problem?