3.6L ESS Aux Battery Bypass

Dkretden

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Or you could run a jumper and disconnect ESS negative and just run the Jeep with the one battery but I don’t believe that the one battery will support using ESS as it’s designed but if you disable ESS kicking in by what ever means it should run fine on just one battery
This is what I am getting to....... it’s about jumping the Jeep.....

‘the are folks who swear that you cannot jump a JL with a battery jumper IF you have a totally shot Aux battery. IF that’s true, you MUST jump with jumper cables, they say...... it is also said that you CANNOT start a JL if the aux battery is not connected or dead.

however, if what is said in the last few posts is true, all one needs to do is disconnect the aux negative cable and jumpy the JL with “whatever method” you choose. Then, push the ESS off button and drive to the dealer to get a new battery or something (forgetting about the n1/n2 jumper solution for a moment.... assume that you don’t want to do this).......

If all of this is true, it’s a huge insight to me.......





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cbrenthus

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I'm confused. (often) Doesn't the Jeep need to have a good aux to start? How does that happen without jumper?
Nope - during startup, the PCR isolates the batteries for about 100th of a second to check the voltage on the AUX battery for ESS. If the voltage on the battery is not good (or 0, as in my case), then it throws an error to service the ESS system and disables ESS. Now, I have an April build '19, so maybe they changed something in the ECU and the earlier or later models won't start, but that's how I'm running and have no issues ;)

Now, if you're AUX battery goes bad, you likely may not start because the AUX battery will take the main down with it if it goes bad due to the batteries being in parallel when the vehicle is off.
 
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Jebiruph

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Or, as I've mentioned, if you don't like ESS and want a single battery, just disconnect the AUX negative. You'll get a message after starting to service ESS, but it goes away quickly, and the ESS light will stay on, but you don't have to hit the button anymore. I've been running like this for a month or two and love it!
I've been watching the gladiator forum in anticipation of getting one and noticed that they are not reporting battery issues to the extent that battery issues are being reported on this forum. Now that I have one, testing this was high on the list. After reading your post, I tested and can verify your results, my gladiator will start with the aux negative disconnected and no other modification, then indicates an ESS error after starting. So thanks for posting.

What this means is that a bad aux battery should not prevent my gladiator from starting, so it will not need a fused jumper or the PCR unplugged. I suspect a bad aux can still drain a good main battery and vice a versa, but jump starts shouldn't need the extra time to build the charge in the aux battery.

My JL was manufactured on 2/28/18 and my JT on 11/16/19, so something changed in between the those dates. @cbrenthus , what's your build date? And anybody else that wants to test, post your results and build date.
 
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Jebiruph

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Nope - during startup, the PCR isolates the batteries for about 100th of a second to check the voltage on the AUX battery for ESS. If the voltage on the battery is not good (or 0, as in my case), then it throws an error to service the ESS system and disables ESS. Now, I have an April build '19, so maybe they changed something in the ECU and the earlier or later models won't start, but that's how I'm running and have no issues ;)

Now, if you're AUX battery goes bad, you likely may not start because the AUX battery will take the main down with it if it goes bad due to the batteries being in parallel when the vehicle is off.
And I see you answered my post while I was typing it.
 

Dkretden

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@Jebiruph
So then, it’s true that by simply disconnecting the negative aux cable I can jump a JL with a battery pack like any other car? I.e. not have to worry about the sacrificial load of the au battery wanting juice during a jump?
 
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Jebiruph

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@Jebiruph
So then, it’s true that by simply disconnecting the negative aux cable I can jump a JL with a battery pack like any other car? I.e. not have to worry about the sacrificial load of the au battery wanting juice during a jump?
With a 2020 JLUR, I would expect you to have the updated ESS system and that it will work as you describe.
 

c2m2h3

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Jerry,

What specifically is the updated ESS System ? Does this system not require a “jumper” ?
 

MadDog27

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Just went into my garage. I removed the neg on the Aux battery and cranked it. Mine started without any issues.
Build date for mine: 10/18
 

jeepdabest

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@cbrenthus Mine started too! But after reconnecting and restarting it still shows service error. Will this go away when I drive??
 
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Jebiruph

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Jerry,

What specifically is the updated ESS System ? Does this system not require a “jumper” ?
Yes, it appears Jeep has updated the ESS System so it doesn't require a jumper.
 
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Jebiruph

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Will the ESS error go away after reattaching? Mine is showing error.
I haven't got that far yet, but it typically can take multiple on/off cycles to clear an error light.
 
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Jebiruph

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I haven't got that far yet, but it typically can take multiple on/off cycles to clear an error light.
I've tried 10 on/off cycles and still have the malfunction indicator on. So anyone wanting to test may want to wait until we figure out how to turn the error off.
 

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