3.6L ESS Aux Battery Bypass

[Fudster]

Ok, so I’ve read that some people are taking the positive from the aux battery and relocating it to the large battery. Would this jumper still be required?

Assuming your Ecodiesel's electronics are like that of the 3.6L, the jumper's role is to constantly connect the two batteries in parallel. Without it the two batteries are connect in parallel at all times but engine cranks and ESS events. This jumper step though still taps the aux battery (and main battery) for power.

Relocating the positive from the aux battery to the large battery makes the jumper moot, but has a different effect: it takes the aux battery out of the picture. The aux battery no longer gets tapped for power.

In either case, disable ESS events from occurring or you'll be tapping your main cranking battery in ESS events and could risk depleting of cranking power at the end of the ESS event.

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[TJ_HOOKER]

Assuming your Ecodiesel's electronics are like that of the 3.6L, the jumper's role is to constantly connect the two batteries in parallel. Without it the two batteries are connect in parallel at all times but engine cranks and ESS events. This jumper step though still taps the aux battery (and main battery) for power.

Relocating the positive from the aux battery to the large battery makes the jumper moot, but has a different effect: it takes the aux battery out of the picture. The aux battery no longer gets tapped for power.

In either case, disable ESS events from occurring or you'll be tapping your main cranking battery in ESS events and could risk depleting of cranking power at the end of the ESS event.

Thanks. I’ve got it disabled through the tazer options.

 

[zrickety]

Anyone has done this? Is it a safe way to get rid of the aux battery headache?

https://www.jlwranglerforums.com/forum/threads/aux-battery-ess-system.85696/post-1792466

 

[Jebiruph]

Ok, I kinda thought so. That will be the way I go I think. I have the aux battery out, leads taped off for now and a piece of buss bar between n1 and n2, but I like the thought of having the positive cables run to the main battery and eliminate the negative cable altogether.
I know the buss bar looks ghetto, it was more of a test fit with some old 100a bar I had laying around

Your buss bar connects the main battery (N2) to the system electronics (N1). That's all you need when you remove the aux battery. At this point moving any aux battery cables to the main battery is redundant.

Having a fuse in the jumper is for when the aux battery is left in the vehicle and it's possible for the aux battery to get shorted to ground through the jumper. Even if you have the aux battery disconnected, there's still a chance that someone could reconnect it and accidentally short a disconnected main battery positive cable to ground which then shorts the aux battery positive to ground through the jumper.

 

[cbrenthus]

Once again, simply disconnect the PCR, DONE! Need to reconnect the AUX for a boost or warranty work? Simply reconnect the negative. I don't know why anyone would make this harder than that I've been running this way for ~2 years on both my Jeep and Pacifica and it works great! Here is the thread with pics I did for the Pacifica forum, please note the PCR for the Jeep is behind the passenger side front wheel liner on the firewall.

https://www.pacificaforums.com/thre...-just-off-the-main-with-no-errors-pics.47626/

 

[Jebiruph]

Once again, simply disconnect the PCR, DONE! Need to reconnect the AUX for a boost or warranty work? Simply reconnect the negative. I don't know why anyone would make this harder than that I've been running this way for ~2 years on both my Jeep and Pacifica and it works great! Here is the thread with pics I did for the Pacifica forum, please note the PCR for the Jeep is behind the passenger side front wheel liner on the firewall.

https://www.pacificaforums.com/thre...-just-off-the-main-with-no-errors-pics.47626/

More people might do this if it was easier to get to. I've got pics in the second post of this thread https://www.jlwranglerforums.com/forum/threads/3-6l-ess-dual-battery-consolidated-information.25377/

 

[Jebiruph]

Once again, simply disconnect the PCR, DONE! Need to reconnect the AUX for a boost or warranty work? Simply reconnect the negative. I don't know why anyone would make this harder than that I've been running this way for ~2 years on both my Jeep and Pacifica and it works great! Here is the thread with pics I did for the Pacifica forum, please note the PCR for the Jeep is behind the passenger side front wheel liner on the firewall.

https://www.pacificaforums.com/thre...-just-off-the-main-with-no-errors-pics.47626/

Is the Pacifica experience with this system similar to the JL/JT experience, do they have the same issues and failure rates?

I would expect them to not have the issue of shorting out the main battery positive cable and blowing the N3 fuse as much as I doubt that they dink with their battery connections as much as JL/JT owners.

 

[cbrenthus]

Is the Pacifica experience with this system similar to the JL/JT experience, do they have the same issues and failure rates?

I would expect them to not have the issue of shorting out the main battery positive cable and blowing the N3 fuse as much as I doubt that they dink with their battery connections as much as JL/JT owners.

Yes, the Pacifica forums aren't nearly as busy as this one, but there have been several AUX failures. The 3.6 engine and electrical system is identical to the JL 3.6. I know because I have both. The fuse box is the same as well, and I had to seat the fuses on the pacifica. Even the steering wheel is the same - they look different, but the size, shape, and control buttons are all the same, which is nice because when I go from one vehicle to other everything is the same. I can also stock up on oil and filters.

 

[ps2baseball]

This is a terrible feeling, like you’ve somehow fried the brain of your Jeep, but it’s almost certainly fine. The JLs do all kinds of strange stuff when battery levels drop below critical levels. just disconnect the battery, fully charge it, reconnect, and see if it will start up. Mine did, but continued to throw some codes, but those went away following a reflash to reintroduce the Jeeps brain to the ABS system.

So after this initial jump, things have been running fine. 0 issues.

 

[entropy]

Just playing devils advocate here.

Why not simply use the tazer or wtver to disable ESS and buy a solid main and aux battery combo?

Jeep should run fine and the aux battery would give you a few extra amp hours. It is not much, but some.

 

[Puch]

I've seen quite a few posts related to failed Aux batteries causing flaky or dead electronics, stalling and failing to start/auto restart. I've come up with a simple way to temporarily bypass a bad Aux battery (also blown PCR fuse or bad PCR) and get back on the road. Warning - this post contains a lot of informed assumptions, so post your related experiences to help validate or invalidate any information I've provided.

Here's a picture of my bypass kit. The jumper is used to connect the N1 terminal to the N2 terminal. I wanted to be able to install the jumper securely, but still be able to quickly disconnect it. A fused jumper seemed to be the best and cheapest way to go. Removing the fuse is a simple way to disconnect the jumper and it protects against overloading the wire. I don't know how much current will pass through the wire, so I used the largest I could find.

6/26/2021 Update - Many have reported that the 30A fused jumper shown in this picture has not been adequate for their JL. Use the highest capacity fused jumper you can find and make sure the fuse is not rated too high for the wire, otherwise the wire will melt before the fuse blows.

Here's how I tested the bypass. I disconnected the Aux battery at N1 and the ground wire at the Main battery negative terminal to simulate a bad aux battery. The voltmeter confirms the disconnect with low voltage at N1.

Here's a shot of the dead instrument panel due to the disconnected Aux battery.

Here's the jumper installed between N1 and N2, voltmeter shows the Main battery voltage at N1.

Here's the live instrument panel.

Here's the instrument panel after starting, only error indicated is open hood.

For those interested, following are some diagrams to illustrate how I understand it works. (See this thread for additional information on the dual battery system https://www.jlwranglerforums.com/forum/threads/3-6l-ess-battery-diagram.14401/)

Here's the battery voltages on a working system, the PCR is connecting the batteries in parallel, both batteries providing power to everything. Normal operation is verified with 0 volts between N1 and N2.

Here's the effect of a failed Aux battery, no power to critical electronics. This should be verifiable by a voltage difference between N1 and N2.

Bypassing is accomplished by jumping N1 to N2. This diagram illustrates the jumper getting power back to the critical electronics.

(updated 04/13/2019)
Additional 3.6L ESS system information is available here.
3.6L ESS Dual Battery Consolidated Information
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-dual-battery-consolidated-information.25377/

Hello, jumping over from the gladiator site.
I have a 2020 sport and positively hate the start/stop feature. When I started having error messages show up, I immediately purchased two new batteries(aftermarket) and installed them myself. I also have no trust that a dealership will fix it correctly the first time so I did it myself. All was good for about 1 month and a couple hundred miles and then the @! showed up and then went away after a restart.
Now I’m determined to eliminate the f’ing aux battery forever, but dont want to spend the $ on a dual setup.
my thought was to just run the + and - to the main batt. Then I read that this trick only works for 6 cycles before the pcm…..pcr…..whatever, notices identical voltage for both batteries and causes more problems.
Has anyone consider attaching the aux + and - to the main batt but using a diode (or a few) permanently placed in line to drop the voltage readings slightly from the Aux battery cable? This could trick the pcm….pcr…..whatever into thinking it still has two batts.
Maybe a stupid idea but I thought I would throw it out there.

 

[dmurray]

my question is less like/dislike of the start/stop "feature". I suppose it has some arguable benefit, in some cases. maybe.
Mine stopped working (some time ago).. Usually never even tries to "activate" cuz I typically don't seat-belt up. No warning lites though... Then when gas prices went all Biden on us, I tried to use it for my daily drive --- yes, even if I had to use the despised seatbelt and all. No warning lite, and no start/stop. Took to dealer (still under warranty) and they did "something" that caused the warning lite to come on, but said it needed a new Aux battery, which was on a long backorder with no end in sight. OK that really bites. I now have an amber warning lite on my dash that I never had before. and it still doesn't work.

It's a Battery! I don't understand why I can't just have the main battery tied to it as shown in the originators post, and have it just work. Mine is a daily driver. I don't do offroad (sorry) not do I have reefers or other aux power loads.

so the SHORT question is: will this jumper fix allow the ESS to function? or at least get rid of the annoying warning lite? (and I think the buss-bar concept would be more straight forward for my use case) --- but will it WORK?

 

[Jebiruph]

my question is less like/dislike of the start/stop "feature". I suppose it has some arguable benefit, in some cases. maybe.
Mine stopped working (some time ago).. Usually never even tries to "activate" cuz I typically don't seat-belt up. No warning lites though... Then when gas prices went all Biden on us, I tried to use it for my daily drive --- yes, even if I had to use the despised seatbelt and all. No warning lite, and no start/stop. Took to dealer (still under warranty) and they did "something" that caused the warning lite to come on, but said it needed a new Aux battery, which was on a long backorder with no end in sight. OK that really bites. I now have an amber warning lite on my dash that I never had before. and it still doesn't work.

It's a Battery! I don't understand why I can't just have the main battery tied to it as shown in the originators post, and have it just work. Mine is a daily driver. I don't do offroad (sorry) not do I have reefers or other aux power loads.

so the SHORT question is: will this jumper fix allow the ESS to function? or at least get rid of the annoying warning lite? (and I think the buss-bar concept would be more straight forward for my use case) --- but will it WORK?

If the dealer said it needed a new aux battery, they probably disconnected the old one which would trigger the error light. You can try pulling fuse F42 (and clearing the error code if needed) to get ESS working with just the main battery. https://www.jlwranglerforums.com/forum/threads/jumperless-aux-battery-bypass.95945/

 

[AnebuR]

For anyone with a 2018 who had TSB 18-092-19 completed (Power Control Update), which supposedly allows starting just off the main battery if the aux one is shot, did anyone confirm that actually works? Recently started getting the ESS unavailable light. Wondering if it's safe to let my aux battery crap out and just leave it there without further action.

 

[correfe]

For anyone with a 2018 who had TSB 18-092-19 completed (Power Control Update), which supposedly allows starting just off the main battery if the aux one is shot, did anyone confirm that actually works? Recently started getting the ESS unavailable light. Wondering if it's safe to let my aux battery crap out and just leave it there without further action.

It definitely works.
I have had my "avengers" light on for a while and the negative disconnected from AUX battery.
Jeep starts right up.

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