I figured I would post this up incase it is a precursor to a bigger issue down the road.

The ECO Button is acting erratic. I'm not real broken up about it but it is happening nevertheless. Sometimes when I start the car it does not illuminate. Sometimes it illuminates after a few minutes and sometimes it never illuminates. Other times it functions as normal.

Any ideas?

 

Weak battery?

 

Everything else is functioning normally.

 

The separate ECO battery perhaps. Think the ‘15 still has the 2nd battery?

 

Yes, that is almost certainly the cause.

 

My switch had to be replaced after about 2 years of ownership. It just completely failed. That is the only thing I've had cause a problem on the car to date, however it wasn't a huge issue (i.e. I could still drive the car, but I couldn't shut off ECO since the switch failed).

 

I noticed it was 95F. in your town as I type this .

ECO doesn't work if it is too hot out & the car needs to keep the a/c running. (Too cold too, but I'm sure THAT isn't your issue.)




Can't comment about the light as we switch the car into DYNAMIC without looking, every time we start.

The ECO battery failing is a probable cause, though.

 

Thanks for all the replies. What else is run off the second battery?

 

AIUI, the second battery is only used to keep the car "alive" during the stop phase - the main battery is used to start the engine.

 

I will add that it's totally optional if you don't mind losing the ECO function. Many here have taken it out of service for that very reason.

 

Not quite. If that were the case then disconnecting the smaller battery would not disable the ECO system - which it does. No small battery connection/voltage, no stop/start. Absolutely no other system is affected by disabling the ECO system.
the 2016 and later cars do not have the second battery.

 

So if my second battery goes bad, I can just ignore it, right? Or should I remove it and leave it out. Never use start stop, never will.

 

It depends on the logic programmed into the system. If the small battery is solely for keep-alive, the system may disable ECO if it detects that it can't keep the car alive. This is the case on single-battery vehicles if the voltage is detected as too low.

 

Er, yes it would - if there's no second battery to maintain "essential services" the car engine won't stop or you'd lose everything - perfectly logical. They obviously changed the logic when they dumped the second battery.

 

I've assumed that they switched to an ultra-capacitor, which are designed specifically for Start/Stop applications.
https://www.maxwell.com/blog/ultraca...ine-start-stop

That's the opposite of the way the ECO system works on 2-battery cars. The 2nd smaller ECO battery is used to power the car's electronics, while the main battery is only used for the starter motor. (Source: OzXFR's repair manual - explains this in detail.) Thus the electronics don't see the voltage drop caused by the starter motor.

Looks like the ultracapacitor is used to power the starter, while the main battery powers the rest of the car, in more modern implementations. No idea if Jag does that.

 

A few questions on this topic from a relative newbie .Owner, 2016 base model, purchased used, 23K miles. Mainly driven on weekends.

1. My eco button is always yellow but I read something in the manual about the button being green. If the car is supposed to "shut down" at traffic stops (the way I hear other cars do like Mercedes, etc.), mine does not. as an FYI, I was having trouble with the key-fob last month (working intermittently) to lock/unlock the doors. I replaced the key-fob battery and problem ceased.
2. Being a 2016, do I have 2 batteries? I located the one in the hatch, which I assumed was the sole battery.
3. Does anyone use a battery tender if using their car as a weekender?

Thank you.

 

- the light on the ECO button is never green. When the yellow light is ON the ECO system is not active, meaning that the engine will not stop and restart automatically (lucky man! - but you can also disable the system permanently - on the 2016 car it is merely a matter of disconnecting a plug).
- the 2016 model has just one battery. The ECO system is slightly different than in the previous models.
- YES. Many or most who do not use these cars daily use a battery maintainer to keep the battery at full charge. The CTEK unit seems to be the preferred maintainer. Instructions for a permanent connection to the one-battery system can be found under threads with " CTEK". My car is connected always when not in use. Once you install the CTEK wiring, it takes about 3 seconds to connect, if you are slow.

 

I think you have this backward. Illuminated=On, not illuminated=Off.

 

And even if the light is on the car reserves the right to not do stop/start if it deems it "inappropriate" (for whatever reason - cold engine, low battery, etc). The manual lists the circumstances when the car will disable stop/start.

 

+1. Also, no secondary battery in MY16+.