Hello …

I am new here and but have been lurking for a year and a bit. I have a 2015 Jaguar XJL and I love the car. Over the past few months the ECO function has been faulty with the car. When I come to a complete stop the ECO function activates shutting the engine down but in the same instance it will start up again. This occurs at every complete stop. I do not have any of the load demanding equipment on like the AC or other load hungry options. So the load on the battery is minimal.
I know there has been a few threads written on this issue that I have read but I have not really noticed any clear diagnosis of the ECO fault.
I took my car to a Jaguar specialist here in Ottawa Canada ( not dealer) and they had mentioned that there is a black junction box located near the small battery in the boot (trunk) that has a series of relays in it that it has a hand in controlling the ECO function. They are suggesting that this junction box is faulty and needs replacement. This black junction box costs about $500.00 + the labour to install it....
Just wondering from other forum members who have experienced this problem if they have had this as a solution to the problem or not.

Thanks in advance,
R27

 

I had the same problem and code revealed it was the power module. My nav/audio system would reset during the event as well. I just removed the negative cable from the small battery and never looked back. You will get a small amber ECO indicator on the display indicating the ECO mod is disabled but everything else works and the annoying start/stop is gone!

 

tjankovs.....thanks for the response. In appreciate it.

 

I think one or both of the batteries is past it. How old are they? If as old as the car, they’re done.

 

Mark...thanks for this. I was actually reading in the F-type forum and they have a similiar power set up. I have always put a tender on the large battery and assumed by the common connection that the small battery would charge as well. I have read that one guy has found a solution to put the tender on the small battery over night and the ECO fault seems to correct itself. I have placed my tender on the small battery and will report back if this corrects the problem.
That being said I believe the large battery has been there since day one however, I have paperwork that the small battery was changed when I purchased the car in 2017.

This actually bring up another question ...do you always go with dealer supplied batteries or do you replace with a decent alternative grade at a cheaper cost ?

Thanks in advance...

 

Mine is also a 2015, and I had a problem where the engine would stop, and then start after just a few seconds. This was fixed by replacing the main battery. I used an AGM from Walmart, Everstart H8 AGM.

 

I have read from other posters that you really need to have an AGM battery if you don’t.

I also ran across this TSP but it sounds like something you have to do with the dealer because it requires their diagnostic software system.

https://static.nhtsa.gov/odi/tsbs/20...96426-1020.pdf