'21 Rubicon Battery issue?

[HOBsc]

Hey all. Newbie here and new to Jeep. Hope I can find some help here.
Bought a 2021 Wrangler Rubicon w/ 45k miles about 3 weeks ago.
Left the dealership and about 10 miles down the road the vehicle shut down completely. No power, no start, no nuthin'. Dealer towed it back and replaced the battery....they were supposed to do that before I picked it up but thsts another story. Fast forward to today....jumped in stepped on the brake pushed the starter button.....nothing. Only thing that worked was the dome light. I figured it was battery again. Hooked up my booster and battery tested fine. I removed the positive cable for about 10 minutes, reinstalled cable and all was well. Brought back to dealer and they tried to pull codes but nothing showed. Maybe codes cleared when I unhooked positive cable?
Anyway.....has anyone else experienced something like this? Super frustrating being as I've only had it 3 weeks.
Any help would be appreciated!!

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[Valpo Jeep]

They replaced the main battery and should have replaced BOTH batteries. Your AUX battery is dead. See if they will make it right and replace the smaller AUX battery.

AUX controls the start stop system and will leave you stranded if dead no matter how good the main battery is. There are ways to remove the second battery from the system but I am not versed in that.

If you have to replace it yourself then there are 2 ways to the battery. Complicated way is from the top and you have to remove the fuse panel. Easier way is through the wheel well after you remove the passenger fender liner.

 

[Reinen]

Sounds like they let the batteries die on their lot which caused your first problem. The JL has a lot of always-on electronics that will kill the batteries if it just sits parked and never recharges. If you ever need to let the Jeep sit for a while you should put a trickle charger on it to counter the draw of the always-on electronics.

Then it sounds like they only replaced the Main and not the Aux. You should always replace both batteries at the same time or you'll go through a lot more batteries than you should. They function as a pair so if they're not working adequately as a pair, replace both regardless if one still tests "good". That actually means almost bad but not quite and it will damage your new battery.

Aux does more than control the start/stop system. It powers the electronics during cold starts to keep them from glitching during the starter power draw.

There is a trick though.
If you press the Start button twice the Jeep will attempt to start using only the Main battery. It's a 2nd chance workaround if your Main still has power but Aux doesn't.

 

[racerdude90]

There is a trick though.
If you press the Start button twice the Jeep will attempt to start using only the Main battery. It's a 2nd chance workaround if your Main still has power but Aux doesn't.

Good info!

 

[Reinen]

Good info!

I should add that the most common way to be in the situation where Main can still provide power but Aux can't is when both batteries are bad/dead but you're getting a jump start to Main.

Remember that the batteries isolate during all engine start events. In a cold start Main powers the starter and Aux powers the electronics that manages the start. And you're only jumping one of them. So you may need to press Start twice to only use your jumped Main.

 

[HOBsc]

Sounds like they let the batteries die on their lot which caused your first problem. The JL has a lot of always-on electronics that will kill the batteries if it just sits parked and never recharges. If you ever need to let the Jeep sit for a while you should put a trickle charger on it to counter the draw of the always-on electronics.

Then it sounds like they only replaced the Main and not the Aux. You should always replace both batteries at the same time or you'll go through a lot more batteries than you should. They function as a pair so if they're not working adequately as a pair, replace both regardless if one still tests "good". That actually means almost bad but not quite and it will damage your new battery.

Aux does more than control the start/stop system. It powers the electronics during cold starts to keep them from glitching during the starter power draw.

There is a trick though.
If you press the Start button twice the Jeep will attempt to start using only the Main battery. It's a 2nd chance workaround if your Main still has power but Aux doesn't.

Thanks for the info! That's more than the dealer told me even after I asked the questions. You are correct that the batteries went dead on the lot. So why is it that the Jeep actually needs two batteries? I get what your saying but most other cars with the same or more electronics only use one?
Dumb question coming.......where is the Aux battery located? Can I change it myself? I'm pretty mechanically inclined but a Jeep newbie so I'm just trying to understand. Thanks!

 

[HOBsc]

Ok. I searched for location of the Aux battery. Question now is......
Is it easier to remove the fender flare to change the battery or go through the top?

 

[Rhinebeck01]

Ok. I searched for location of the Aux battery. Question now is......
Is it easier to remove the fender flare to change the battery or go through the top?

You risk doing lots of damage and expense going "through the top". Even seasoned Techs do not do it this way.

Fender flare pull is one way, fender liner peel is another way and what the dealer techs do and are recommended to do by Stellantis. Another way, I call the peeky boo way is yet another way... If you are a small frame guy or gal and are adept at working in tight places, the peeky boo way is to be considered first of all.

Anyway, do read here for info on doing the Aux battery change... You will read info that will help you keep from lets say screwing up and or making the Aux battery change out more of a big deal then it really is.

https://www.jlwranglerforums.com/fo...ent-the-easy-way-pull-the-fender-flare.56807/

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[HOBsc]

Thank you! Much appreciated!

 

[Rhinebeck01]

@HOBsc

I'd also read here before you change out your Aux and Main battery..
https://www.jlwranglerforums.com/forum/threads/🔋🔧-main-battery-replacement-talk-jl-jt-🪫.100534/

 

[chadk77]

Pull the F42 fuse and it should allow you to use the main battery to start the Jeep.

https://www.jlwranglerforums.com/forum/threads/jumperless-aux-battery-bypass.95945/

 

[HOBsc]

Pull the F42 fuse and it should allow you to use the main battery to start the Jeep.

https://www.jlwranglerforums.com/forum/threads/jumperless-aux-battery-bypass.95945/

Thank you! I've never understood why 2 batteries are necessary but now I get it. I dislike that that ESS anyway and would be glad to disable without pushing the button. Hopefully I can get there. Changing the aux battery should be no issue for me but if the JL functions just fine without it why is it there?
I really appreciate all the help. Learned more in the past 12 hours on this forum than I did from the dealer. Needless to say I will make no more trips to the dealer as they've jerked me around the past 3 wks. Even if I asked again to replace the aux, they won't. They claim it's fine and "just can't see anything wrong"

 

[Easttnrhino]

My 21 rubicon does not have auxiliary battery, but it’s the 3.6 is e torque engine it has big batteries on frame rail and the battery under the hood. When ordered the dealer said at that time it was the only engine available with the XR. I dread it when and if it has problems. That being said is your the e torque motor?

 

[HOBsc]

H

My 21 rubicon does not have auxiliary battery, but it’s the 3.6 is e torque engine it has big batteries on frame rail and the battery under the hood. When ordered the dealer said at that time it was the only engine available with the XR. I dread it when and if it has problems. That being said is your the e torque motor?

Hmmmm......I don't belive so but I wouldn't know for sure. What's an easy way to tell? The vehicle is at home today so I'll need to check after work.

 

[Easttnrhino]

the e torque engines have a big battery pack under Jeep just across from gas tank drive, also under the hood right in the center top of motor the alternator is huge I think I remember reading it actually a 48 volt generator, it what starts my motor when using the stop start. I did not remember if it e torque on the hood.

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