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URGENT help needed. Can't start my 2018 JL

James_a

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When the vehicle is off the batteries are in parallel and can be charged with a charger or with another car running and jumper cables connected. I did not need to disconnect the two batteries to jump or charge with my maintainer, after the volts were high enough. If the voltage is too low on the battery, depending on your charger, you can have it connected all night and it wont charge the battery. The battery may need to be above a certain voltage before your charger does any charging, mine gave an error saying the battery wouldn't hold a charge, thus the need for another vehicle and jumper cables to get the batteries above the threshold.

I believe others here have had their batteries changed under warranty but I do not remember the thread offhand.
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kantho

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Unfortunately many people have only been getting about 2 years out of the stock batteries before they go to shit, you may be there. If you have to replace, replace both of them.
Thanks for that info. Any chance that would be covered under warranty?

After attempting to change both batteries independently now on the tach and speedo are twitching. No lights at all. Makes no sense to me.
 

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@kantho Having read the comments above, some things said may be incomplete or misleading, if not wrong.
  • On the 3.6L, back in 2018, if the ESS/Aux battery lacked charge the vehicle would not crank, no matter how much energy was in the main battery. If it did, both batteries would be hooked up in parallel prior to attempting the crank. This is why, back then, you could crank your 2018 3.6L JL with only a charged ESS/Aux battery connected, but not only a main battery connected.
  • Recently, members on the board have reported that a flash by the dealer to 2018s, along with more recent model year 3.6's, have experienced a change to this cold crank logic such that no longer, at least on the second try, will a dead ESS/Aux battery prevent you from cranking provided the main battery has adequate power. This main battery having power though may not be the case though as both batteries are connected in parallel when the 3.6L is at rest such that a dead (and possibly defective) battery may steal power from a good one in vain, rendering both dead.

    If you want more 411 on the flash let me know, I'll send you a link.
  • The voltage of the ESS/Aux battery doesn't require both posts on the main battery to be freed of cables, just one, say the negative post. Removing cables from both main batteries posts isn't bad and will work too, it's just more work.

    Because the batteries are connected in parallel at rest, putting energized jumper cables on the main battery alone charges both if they are capable of holding a charge.

    Let me know if I may be of further help.
 

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Thanks for that info. Any chance that would be covered under warranty?

After attempting to change both batteries independently now on the tach and speedo are twitching. No lights at all. Makes no sense to me.
Hey Karl:

If you have ability to measure the voltage with a meter, what voltages do you get:
  • With all cables intact and your meter on the main battery (both batteries), and
  • Disconnecting all the cables from the main battery's negative post and putting a voltage meter's positive prong on the main battery's positive and the meter's negative post on the main battery's negative posts (a voltage test of the main battery), and
  • With just the main battery's negative post's cables disconnected as above, placing your voltage meter's positive prong on the main battery's positive post again, and the voltage meter's negative prong on the dangling cable's connection point (the ESS/Aux battery)? Don't forget to reattach those cables back to the main battery's negative post and tighten them down a bit.
 

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JimLee

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Thanks for that info. Any chance that would be covered under warranty?

After attempting to change both batteries independently now on the tach and speedo are twitching. No lights at all. Makes no sense to me.
I believe they are covered but not as long as the regular warranty as they are considered a consumable or service item (such as a filter or tires), I think some have had theirs replaced and had to pay a surcharge or prorated charge.
 
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kantho

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@kantho Having read the comments above, some things said may be incomplete or misleading, if not wrong.
  • On the 3.6L, back in 2018, if the ESS/Aux battery lacked charge the vehicle would not crank, no matter how much energy was in the main battery. If it did, both batteries would be hooked up in parallel prior to attempting the crank. This is why, back then, you could crank your 2018 3.6L JL with only a charged ESS/Aux battery connected, but not only a main battery connected.
  • Recently, members on the board have reported that a flash by the dealer to 2018s, along with more recent model year 3.6's, have experienced a change to this cold crank logic such that no longer, at least on the second try, will a dead ESS/Aux battery prevent you from cranking provided the main battery has adequate power. This main battery having power though may not be the case though as both batteries are connected in parallel when the 3.6L is at rest such that a dead (and possibly defective) battery may steal power from a good one in vain, rendering both dead.

    If you want more 411 on the flash let me know, I'll send you a link.
  • The voltage of the ESS/Aux battery doesn't require both posts on the main battery to be freed of cables, just one, say the negative post. Removing cables from both main batteries posts isn't bad and will work too, it's just more work.

    Because the batteries are connected in parallel at rest, putting energized jumper cables on the main battery alone charges both if they are capable of holding a charge.

    Let me know if I may be of further help.
Good information definitely. My fear is that without power I won't be able to unmarry my ZAutomotive Taser Lite and I will need to do that before any dealer flash. I wonder if there's a chance that flash has been done by the dealer at my oil change there a couple months ago. Do they always update the firmware or only if there's a problem that the firmware fixes. Is there a way to tell if it's been done?
 
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kantho

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Hey Karl:

If you have ability to measure the voltage with a meter, what voltages do you get:
  • With all cables intact and your meter on the main battery (both batteries), and
  • Disconnecting all the cables from the main battery's negative post and putting a voltage meter's positive prong on the main battery's positive and the meter's negative post on the main battery's negative posts (a voltage test of the main battery), and
  • With just the main battery's negative post's cables disconnected as above, placing your voltage meter's positive prong on the main battery's positive post again, and the voltage meter's negative prong on the dangling cable's connection point (the ESS/Aux battery)? Don't forget to reattach those cables back to the main battery's negative post and tighten them down a bit.
Looks like 13.2 across the combined terminals, 13.8 across just the main battery with negative cable assembly removed and then 11.7 with the main battery disconnected which should be just the AUX battery at 11.7. Is that so low it will prevent starting?
 

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Looks like 13.2 across the combined terminals, 13.8 across just the main battery with negative cable assembly removed and then 11.7 with the main battery disconnected which should be just the AUX battery at 11.7. Is that so low it will prevent starting?
Hey Karl:

The low voltage on the ESS/Aux battery you report could be (part of) the culprit. It may also be fine in terms of holding or delivering charge, but getting drained by some defective power source, or who knows what. My first guess is that it is defective.

I might take it to the dealer and ask that after charging or replacing whatever battery failed, if any, or however it is fixed, to flash this firmware fix I talked about prior, so that if in the future it is your ESS/Aux battery that is drained, but not your main one, that the rig will, unlike for 2018 3.6L JL's, switch to the main battery to effect the crank and you won't get stranded.

https://www.jlwranglerforums.com/forum/threads/3-6l-ess-bad-aux-battery-no-start-firmware-fix.53608/

There is another fix to this problem from the same forum member that reported this firmware flash. It involves jumpering two electrical connection points within the rig, either permanently or temporarily so the ESS/Aux battery is never isolated, even in the pre-flash fix examination of the rig by the computer of its ESS/Aux battery in isolation.

https://www.jlwranglerforums.com/forum/threads/3-6l-ess-bad-aux-battery-no-start-firmware-fix.53608/

IMHO it is rendered somewhat obsolete by the flash, but the flash costs $, on top of a replacement ESS/Aux battery if you go the fix it yourself route. It's good to have a backup of this battery if it turns out that swapping it does not fix things.

If you want the link on how to do this please say so and I'll dig it up for you. I don't think it dangerous but I wouldn't go into the dealer with this hack to be seen by them. I'd also recommend turning off ESS with this hack in place for reasons I am glad to explain to you on request.
 

James_a

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At this point I would have to defer to people with more experience. When I had my issue my batteries combined were down to 4V... If I remember correctly at one point my batteries combined were close to 12v and I was still able to start. However I never tested the batteries voltages separately since performing a jump start solved my issue... I wish I could help out more.

It would be interesting to know what the voltage thresholds are to allow startup.
 

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kantho

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I want to thank everyone for all their help. Great research and good information that I am wading through to slowly learn. Unfortunately some personal stuff popped up so I haven't gotten this resolved yet but I will come back and post when I do.
 
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kantho

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I learned the hard way that those big smart battery chargers won't charge a fully discharged battery. Now I know. :) When the batteries registered 1.5 volts, I assumed my volt ohm meter was bad. So after 2 days of charging, first with a trickle charger to get the voltage above the threshold and then with a big charger, I was able to get voltage up to 11.7 which was enough juice to be able to unmarry my Tazer Lite, start the engine and drive to the dealer.

The dealer promised to get to it within 2 weeks and was skeptical when I spoke of perhaps a hidden warranty on the batteries. So next day they called and told me they had replaced both batteries with new. They also reported all my updates were current and nothing new was flashed into place.

So I am not sure if there's any way to check if the ESS update was already there or not. I am also still not sure if the Tazer Lite which allows me to turn off the ESS by default had any impact on the failure of my auxiliary battery which is clearly tied to the ESS system. Why was my system working one day then 2 days later the battery was at 1.5 volts?

I really appreciate all the help given here. I have learned a lot and hope my experience can help others. If anyone has anything else to contribute, thanks in advance.
 

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So I am not sure if there's any way to check if the ESS update was already there or not.
Do you mean the update Karl that reports being able to cold crank the 3.6L even if the ESS/Aux battery is discharged or absent?...

"A" way to test this is to disconnect this cable in the video below and take it out of the loop and see if the rig cranks. The rest of the cables remain affixed to both of the main battery's posts. This will take the ESS/Aux battery out of the circuit while this cable is detached.



Supposedly the rig will crank on the second try and result in an error code that I cannot guarantee is resolved once the cable I refer to in the above video is reconnected; so maybe no best to try....but this is "a" way. Jeep Informant didn't report problems trying this in the video but it was back in 2018.
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