Electronic Start/Stop disabled second time

[linuxos77]

We have a 2020 Sahara with about 21k miles on it. For the second time this summer the Service ESS light came on upon start up, and ESS was disabled. Curiously both times the summer this happened were after the Jeep sat in direct hot sunlight (for New England) all day. Temperatures around 90 or so. After driving for a bit we noticed the light went away on the next start up. Google'ing around I believe if the system disables due to ambient temperature it says as such versus the service ESS we're seeing. Any ideas?

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[Rustydog]

I think it also disables if the smaller battery gets too low.
Do you also see on startup message something like Auxiliary switches disabled, battery charging?
Of course it disables if the AC is on.

 

[linuxos77]

I think it also disables if the smaller battery gets too low.
Do you also see on startup message something like Auxiliary switches disabled, battery charging?
Of course it disables if the AC is on.

It was with my wife today, so I don't know what errors, she just sent a pic with the A in the circle light on and the screen saying ESS Service Required or something similar, this same thing happened in early July and went away the next start up after stopping an hour or so for lunch. When our AC is on ESS doesn't disable normally, thought the engine will auto start while we're at a light when the condenser kicks on.

 

[Rustydog]

Correct; my error. Mine does the same with AC. Doesn't actually disable.

 

[Rico1111]

It was with my wife today, so I don't know what errors, she just sent a pic with the A in the circle light on and the screen saying ESS Service Required or something similar, this same thing happened in early July and went away the next start up after stopping an hour or so for lunch. When our AC is on ESS doesn't disable normally, thought the engine will auto start while we're at a light when the condenser kicks on.

Also In New England and my JLR has also been sitting in the sun .....Same exact thing has happened and I accredited it to the heat. I believe the aux battery is about to give up the ghost so I made an appointmment. I checked the off road app and the battery was at 14.3 and then when I got in and the lights came on I checked again and it was 14.0 I'm assuming its going. I am still under 36000 so will hopefully have it replaced but at some point I will change them both out to better batteries.

 

[Htfan]

Also In New England and my JLR has also been sitting in the sun .....Same exact thing has happened and I accredited it to the heat. I believe the aux battery is about to give up the ghost so I made an appointmment. I checked the off road app and the battery was at 14.3 and then when I got in and the lights came on I checked again and it was 14.0 I'm assuming its going. I am still under 36000 so will hopefully have it replaced but at some point I will change them both out to better batteries.

Yes, you are correct to suspect your Aux battery. When the dash shows 14+ volts charging most of the time it usually means one or both batteries are weak.

I had this issue before, however after replacing both batteries the voltage now normally reports 12.7v to 13v with healthy charged batteries.

 

[Rhinebeck01]

@Rico1111

When you take your JL to that appt...

Ask to talk to the Service Manager (not Service Writer) . Politely ask Service Manager to provide you with the copies of BOTH, Load Test print outs that the Tech should be seeking / will be seeing, basing decisions on in regard to what needs to be replaced/gets replaced.

You want to do this to assure the Tech actually does load test both and not, not do both and say he did.... which is common/happens..

Doing the aforementioned is especially important for you as your 2018 JL will soon be off of warranty in regard to the batteries. What they miss, do not do or replace you will pay lots of $ for when off warranty...

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