2018 JLUR ESS Electrical/Battery Issue

[ALEX-4LO]

Looking for any input or someone who experience anything like this before.
2018 JLUR 3.6 with 66k miles.
For the past a couple of weeks, I notice cold starts would crank slower. I did not think much of it because I really don't use the Jeep much anymore. A couple of days ago I was driving and got an "engine shut off soon", start stop light and battery light message and my display froze and jeep went limp. Luckily, I was close by my house and was able to park quickly, I noticed white residue on the main battery negative terminal, plus copper discoloration, nothing crazy. I remove the battery and aux to get tested at Autozone, main comes back fine - Aux comes back low and gets a free charge. Pick up 5-7 hours later and install. Turn on jeep (in the garage) and same light display and engine shut off soon message comes on.

Battery is an Optima DH6 AGM, only ~8 months old. Aux battery is ~2 years old (Autozone brand). Still in question, why did this battery cause copper discoloration, thinking faulty battery.
I do have a Tazer and use it to bypass the start/stop button.

I now check and see if I can bypass the aux battery completely and just use the main by removing the aux battery and connecting the positive terminal from aux to the positive main terminal, same issue all lights come on. I then remove the negative line on the main battery that feeds the ESS system. I turn on the Jeep, and same message and lights turn on immediately after starting. So, bypassing the aux battery never worked for me. I turn off the engine and turn on to "run" only position and notice the battery is displaying 11.8V

I replaced the N3 fuse array. installed the "charged" aux battery again and made sure all terminals were properly connected to the main battery and aux battery, start the jeep and engine shut off lights come on immediately.

Working theory:

1. Replace main battery and aux - all new batteries, I guess...
2. Replace IBS sensor and negative battery cable.
3. PCR relay is in question. --- sigh
4. I attached a photo does the negative cable clamp need replacing?

Let me know your thoughts, experiences or a fix. Thanks!

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[kah.mun.rah]

The aux battery in my 2018 JLUR 3.6L went bad and had to be replaced every 18 months.

 

[FF5Cobra]

As for guestion of negative battery post.
looks like clamp is bottomed out meaning it can’t be tightened anymore
I f you can wiggle/ move terminal clamp. That is loose connection that would explain corrosion on terminal.
I use. CRC brand terminal protective Spray on terminals

 

[AndySpill]

I do have a Tazer and use it to bypass the start/stop button.

I now check and see if I can bypass the aux battery completely and just use the main by removing the aux battery and connecting the positive terminal from aux to the positive main terminal, same issue all lights come on.

I'm not sure of what your problem is.

What I am sure of is that you should disconnect the smaller of the two factory cables that attach to the negative post of the main battery and tape up its end, and pull Fuse 42 in the PDC (Power Distribution Center; your fuse box) bypassing the Aux battery.

This will not only simplify troubleshooting your issue, but if you've committed to not running ESS events, as you've indicated, that Aux battery is more than not needed. Better stated, it's more problematic to have than bypass under such "not running ESS" situations..

I cannot see anyone with a dual AGM battery JL running both factory batteries unless they desire to run ESS events, or maybe keep things stock during a warranty period.

I opened a thread a little while ago about people denied dealer service (not warranty service, but paid service) because they bypassed the Aux battery https://www.jlwranglerforums.com/forum/threads/has-it-happened.154662/

After 13 pages of posts, if I remember correctly, one responded said "yes," and all others said no.

 

[morrisl29]

Is it charging?
Can you see what codes are showing?

 

[JL.FR]

Hello, I have the same Wrangler as you, same year (2018), manufactured in July (EU export). I changed the small battery last year (6 years) and changed the large one this year (7 years). I always disabled the ESS (using the button), but I also periodically checked that it was working, until last year when the small battery died. When the ESS stops working, it's almost always a sign that the small battery is dead. Perhaps the quality of EU export batteries is better than US ones? Otherwise, I've never had any problems with the batteries.

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