Hey All -

I recently purchased a 2013 XJ “L” with just under 48K original miles from the 2nd owner.

Immediately knew I needed this one badly - I’m impressed so far. When we were discussing it’s flaws he told me the Eco Start/Stop feature was driving him crazy so he had a tech/mechanic disable it. There were no check engine lights on or major dash warnings so I didn’t think much on it. And we had it pass emission/smog before purchase so I felt comfortable enough that it wasn’t the end of the world and I could live with it being disabled.

About a month has gone by and I’m curious about adding the feature back. Or is that a mistake? I dove into the trunk to see how the tech ended up disabling it and assumed he just disconnected the Aux Battery like most forums recommend. However the negative cable is still connected and don’t see any issues on that front.

I did come across a “lose” connection on one of the wiring harness with a “brown/white and black” wire married to a white connection tip.

Is this what was disconnected to disable to the Eco feature?

Is the Aux Battery bad perhaps?

Im lost after several hours of light research.

Any help is greatly APPRECIATED!

 

I also have the 2013 next year with the V6 SC. (On paper it has more HP than my ‘06 XJ8, but it just doesn’t sound like it!)

I got mine through Carvana since I am about 150 miles away from most dealers and I had already made multiple trips, (And each one being a waste of time.) I figured their convenience, guarantee & warranty were worthwhile.

Their prices were higher but the cars are very immaculate and every time I look at a vehicle, I waste a whole day—so I figured this was a good way to go.

My Eco start also seems to not work but the light comes on or off if I use the button (like it would if working.) But I’ve never ever seen the engine stop. I’m on an archipelago island chain; closer to the equator than most anyone—and the manual does say that if it needs the AC, it won’t shut off. Which could be the case, because lately almost every day feels feels like 100° here!

I could’ve got a check at a dealership but It’d be a day up there a day or more for them to look at it & a day back and I probably would’ve had to pay for a hotel as well. So I figured it wasn’t the end of the world.

However your post has me intrigued so I’ll look to see if I have the same white connector that’s not plugged into anything.

I did have both batteries checked at Napa, they do it in vehicle. First Key Death Hwy After I got the car they couldn’t get a reading on the secondary battery first one was around 60% so I drove to another Napa about 20-25 miles away reading was higher! I had a business trip which took me up north so when I came back inside and been a 300 mile round-trip I’ll check the batteries again and Hillary was 100% and the primary was almost 90%.

I will tell you I ownef an XF and I was able to actually sleep in that vehicle after hurricane Irma hit us and I had the radio going most all night! (I don’t recall exactly when I shut it off but it was for literally hours.) The XJ I have now doesn’t let me keep it on for more than 20 or 30 minutes before it shut off on its own. I believe these cars are power ******!

 

That wire is for shipping only and should have been tucked away and hidden by the dealer during the pre-delivery inspection. If the small AUX battery is good you most likely have something failed in the start/stop system. This is common and on my 2014 after I replaced the AUX battery the start/stop never worked again, I hooked up my SDD and found a start/stop error code. This is a code you won't find with any scanner. You need one that can go very deep into a Jaguar to see.

Brutal one of our factory techs has said this is common and the start/stop system is failure prone. Your better off without it. I know I won't be spending any time or money to get mine working again. It also has nothing to do with emissions testing so no worries there.
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There are lots of folks out there who swear by living without it due to the annoyance of start/stoping the engine. After all, at its most simplest form the feature is stopping the engine for you by way of the braking system - so braking at full stop will shut off engine. Releasing brake will cause the engine to start back up. Seek counter intuitive to me anyway? Why they wouldn’t put more thought into a $70k plus machine when there was better tech out there seems redundant to me.

Thank you for sharing - I now know what that little unplugged wire is!

 

Well they added it to increase gas mileage so it helped with the advertised city/county MPG numbers. I found it out of place on a high end luxury car as it makes noises and causes the car to shudder upon restarting. Not the smoothness Jaguar is known for.
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The Eco Start/Stop system not working was a common issue for years. Mostly for Jags out of Castle Bromwich. I’m including a pdf of the service bulletin from JLR’s TOPIX as there are a lot of ‘unsafe’ web sites supposedly offering it.

 

The Aux battery might be strong enough to keep the lamp in the dash from illuminating a malfunction but not enough to do the proper on off feature. Do not spend time trying to fix it. I wanted it to work badly but I gave up on it. I had a battery installed and worked well for about a month. Now it works randomly when it chooses. If there is not enough reserve voltage it doesn’t work. Constant AC it’s futile. The car stars to smell musty when the compressor stops and the climate will demand it to start shortly after. Not enough time to even the shortest stop lights. Feel free to replace the aux batttery if the dash lamp bothers you but it won’t be long lasting. The original aux battery will work longer. But the system doesn’t work well on the car when the climate control is operating. Windows open is a little better.

 

Thanks much for posting that TSB! It was one I had not seen before.
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