CEL on after possible ESS / Battery issue

[Michellenoel]

Hi! I was parked with my 2019 wrangler unlimited off, and it would not start. My brake pedal felt stiff and when pressing the push to start it clicked once, lit up the dash but never turned over to start the engine. I got a jump and was able to get the car fully on. I drove around for ~30 mins with no issues. I went to the gas station, turned the car off to fuel and it started again no issues. On my way home from there, I was in a drive through and my ESS kicked in while my foot was on the brake and stopped the engine as it always does. When I removed my foot from the brake and it went to start back up, it made a strange sound and my car locked up. The D on my shift knob was flashing. I put the car in park and turned it off because that was all I could do. When I turned it back on, it started but seemed to have to work harder to start. My check engine light is now on. Any idea what the issue may be? At first I thought maybe a battery issue since jumping it worked fine initially, however the ESS causing a stall leads me to believe maybe I am wrong. I know nothing about mechanics of cars please help so I have an idea going to the mechanic of what to expect! Note, I am a younger female and ripe for being taken advantage of at any sort of dealer or mechanic sadly.

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[GATORB8]

Guessing battery on a 19. You have two, a standard 12V battery under the hood, and a little Aux one buried underneath it.

Autozone/Advanced/Oreilly's will read the code for free for you. They'll also test your battery/alternator/starter for free. If you need new batteries, you want to do both. They'll definitely install the standard 12 for free, not sure they'll do the Aux since it's a little tougher.

 

[GATORB8]

Note, when the battery kicks the bucket, the system will go haywire and throw all kinds of codes. If they pull up a bunch of unrelated items, have them clear and restart it with the new battery.

 

[SmallCrawler]

If your 2019 Jeep is equipped with a main and auxiliary battery, and those batteries have not been changed since new, then you will have to get some new ones installed. Just about all modern car/truck batteries have a shelf life of about 3 years now due to parasitic drain from engine computers/sensors etc.

There is a lot of helpful information on this forum about the goofiness of the small aux battery buried behind the front passenger fender, how to bypass or delete it, and so on. But I have made peace with the design and simply press the the electronic stop start (ESS) button to off almost every time I get in the jeep.

From time to time I then monitor the aux battery by scrolling through my center dash information cluster to check on the status of the ESS function. You will know that the aux battery is about finished when you see messages that say it is not ready (when you know it should be charged due to long trips or charging attempts with a battery charger).

Best description I have seen on the forum is to consider the 2-battery factory design, if you have it, as similar to a TV remote. Change both batteries, not just one or the other. It's a goofy design for sure, but it generally works, and all the electronics play nice if you maintain it.

 

[Reinen]

If your 2019 Jeep is equipped with a main and auxiliary battery, and those batteries have not been changed since new, then you will have to get some new ones installed. Just about all modern car/truck batteries have a shelf life of about 3 years now due to parasitic drain from engine computers/sensors etc.

There is a lot of helpful information on this forum about the goofiness of the small aux battery buried behind the front passenger fender, how to bypass or delete it, and so on. But I have made peace with the design and simply press the the electronic stop start (ESS) button to off almost every time I get in the jeep.

From time to time I then monitor the aux battery by scrolling through my center dash information cluster to check on the status of the ESS function. You will know that the aux battery is about finished when you see messages that say it is not ready (when you know it should be charged due to long trips or charging attempts with a battery charger).

Best description I have seen on the forum is to consider the 2-battery factory design, if you have it, as similar to a TV remote. Change both batteries, not just one or the other. It's a goofy design for sure, but it generally works, and all the electronics play nice if you maintain it.

^ This.

There is a bunch of confusion about Aux being an "ESS Battery". I've been incorrectly sucked into that thought pattern myself. But it's not. I'm an engineer and I went so far as to review the JL's wiring diagram.

Aux is an Electronics & Communications battery. Aux has nothing to do with ESS beyond providing clean stable power to the electronics and network that manages ESS (along with everything else). It is a separate battery that is isolated during engine starts so the high draw of the starter doesn't impact electronics and communication.

Don't bother reading codes at this point. When the Electronics & Communications experience a power brownout they spit out random incorrect codes. They mean nothing other than you had insufficient power to maintain stable system communication.

As @SmallCrawler said, always replace Main & Aux at the same time. They work as a pair and need to be the same age and have the same wear.

 

[SmallCrawler]

^ This.

There is a bunch of confusion about Aux being an "ESS Battery". I've been incorrectly sucked into that thought pattern myself. But it's not. I'm an engineer and I went so far as to review the JL's wiring diagram.

Aux is an Electronics & Communications battery. Aux has nothing to do with ESS beyond providing clean stable power to the electronics and network that manages ESS (along with everything else). It is a separate battery that is isolated during engine starts so the high draw of the starter doesn't impact electronics and communication.

Don't bother reading codes at this point. When the Electronics & Communications experience a power brownout they spit out random incorrect codes. They mean nothing other than you had insufficient power to maintain stable system communication.

As @SmallCrawler said, always replace Main & Aux at the same time. They work as a pair and need to be the same age and have the same wear.

Thanks for that concise clarification, Reinen. I didn't understand the system at the wiring level like you but after considering a Genesis dual battery setup, or an auxiliary delete, I decided to stick with the factory design and replace both batteries. Just did not want to mess with the electronics or warranty eligibility at all.

 

[Rustynail11]

Having the exact same issue and waiting for dealer to call after running a diagnostic. The SA and I discussed and another SA that has a 392 came over and chimed in as well. We all agree it is the crap 2nd battery. Lets see what the test say

 

[Reinen]

Thanks for that concise clarification, Reinen. I didn't understand the system at the wiring level like you but after considering a Genesis dual battery setup, or an auxiliary delete, I decided to stick with the factory design and replace both batteries. Just did not want to mess with the electronics or warranty eligibility at all.

The Genesis dual-battery system certainly has it's place. But that place is in overlanding use when you use your JL's battery for more than starting & operating your JL. Situations where you may drain your battery too much to start your Jeep.

But I think the Genesis approach is old-school at this point. There are better approaches available now. Here's my setup:

• Stock Main/Aux using ESS on-road
  Keeps electronics protected during starts and ESS is an excellent "canary in the coal mine" for battery issues. Every time it engages is a successful battery check.
• Cascadia 4x4 Hood Solar Panel
  This passively counters the parasitic drain of the electronics and insures the JL's batteries are at 100% as often as possible. My batteries are a couple months away from 3 years old and still going fine, which I attribute to the solar panel. We'll see how long they last.
• Portable Lithium Power Bank
  This is what powers my overlanding/camp equipment while I reserve the JL batteries for the JL. The power bank is only recharged when the JL is running or if I connect a folding solar panel. Unlike AGM, I can drain the lithium battery as much as I want without damaging it. Being isolated, even if I drain it completely it will never impact my ability to start the Jeep.

 

[Michellenoel]

Hey all! Thank you so much for your fast replies and input. From what it seems like here, this is likely a battery issue and I should replace BOTH batteries. My jeep is 4 years old and ~53k miles so the batteries have had their wear. I am going to my local autozone tomorrow to have them run the battery test as recommended here. Would they likely be able to tell me what batteries to buy there? Hopefully they can install it, otherwise I will have a mechanic. Lastly, do I have them run the code test before&after battery swap or just after since the faulty battery likely threw random codes out on failure? Thanks again for all the input, you’re probably saving me $100s of dollars due to lack of knowledge on this

 

[SmallCrawler]

The Genesis dual-battery system certainly has it's place. But that place is in overlanding use when you use your JL's battery for more than starting & operating your JL. Situations where you may drain your battery too much to start your Jeep.

But I think the Genesis approach is old-school at this point. There are better approaches available now. Here's my setup:

• Stock Main/Aux using ESS on-road
  Keeps electronics protected during starts and ESS is an excellent "canary in the coal mine" for battery issues. Every time it engages is a successful battery check.
• Cascadia 4x4 Hood Solar Panel
  This passively counters the parasitic drain of the electronics and insures the JL's batteries are at 100% as often as possible. My batteries are a couple months away from 3 years old and still going fine, which I attribute to the solar panel. We'll see how long they last.
• Portable Lithium Power Bank
  This is what powers my overlanding/camp equipment while I reserve the JL batteries for the JL. The power bank is only recharged when the JL is running or if I connect a folding solar panel. Unlike AGM, I can drain the lithium battery as much as I want without damaging it. Being isolated, even if I drain it completely it will never impact my ability to start the Jeep.

More good info. The cost of that Cascadia panel is a little chesty for me. As a retired geezer my Jeep lives in the garage a lot so I just use a trickle charger now and then. But your setup is great for folks who daily their Jeep, regardless if they overland. Thanks again for helping the forum see some good alternatives. The hood solar panel is cheaper than the Genesis for sure.

 

[GATORB8]

Hey all! Thank you so much for your fast replies and input. From what it seems like here, this is likely a battery issue and I should replace BOTH batteries. My jeep is 4 years old and ~53k miles so the batteries have had their wear. I am going to my local autozone tomorrow to have them run the battery test as recommended here. Would they likely be able to tell me what batteries to buy there? Hopefully they can install it, otherwise I will have a mechanic. Lastly, do I have them run the code test before&after battery swap or just after since the faulty battery likely threw random codes out on failure? Thanks again for all the input, you’re probably saving me $100s of dollars due to lack of knowledge on this

Yes, they can tell you what batteries to buy. I'm going to guess the standard answer will be no for the Aux installation, but that doesn't mean you won't luck out and have an Autozone guy go out of his/her way for you.

There are two ways to get to the Aux, digging down to it, and going through the fender liner (this is how the service manual says to do it). I'd recommend watching a video on it on youtube so you are familiar with it.

Note, they cannot just hook up the battery for the test. The batteries are hooked together, so you could get a false "good" if one has enough juice to prop up the other. They can test the alternator and starter how it is, then ask them to pull the terminals and test the main battery by itself. I'd assume you may be able to get a good read on the Aux by testing the terminals that you pull off the main battery (someone correct me if I'm off base there).

EDIT: In case you go to a mechanic, Alldata shows the labor hours as:

Battery, Charge/Test: 0.4 Hours B Skill
Battery, Remove and Replace
*Auxiliary: 1.0 Hours C Skill
*Main: 0.5 Hours C Skill

EDIT: Note, the battery warranty lengths are real indicators of how long they will last.

 

[Reinen]

More good info. The cost of that Cascadia panel is a little chesty for me.

FWIW, The smaller and cheaper Rubicon hood panel can be installed on any JL. It's more than enough to counter the parasitic drain.

The larger Sport hood panel I'm not so sure about. 80w is overkill for countering the parasitic drain and it will still take a long time to charge a dead battery with it. So I'm not really seeing the cost justification. If you need that much power just put a full flat panel on the roof, it's half the price and double the power.

 

[CarbonSteel]

These two batteries have been the best I have had for over the counter. Be sure that you change both of them:

Main - https://shop.advanceautoparts.com/p...6-P?navigationPath=L1*14920|L2*15000|L3*15597

Auxiliary - https://shop.advanceautoparts.com/p...8-P?navigationPath=L1*14920|L2*15000|L3*15597

 

[Fa1321tx]

^ This.

There is a bunch of confusion about Aux being an "ESS Battery". I've been incorrectly sucked into that thought pattern myself. But it's not. I'm an engineer and I went so far as to review the JL's wiring diagram.

Aux is an Electronics & Communications battery. Aux has nothing to do with ESS beyond providing clean stable power to the electronics and network that manages ESS (along with everything else). It is a separate battery that is isolated during engine starts so the high draw of the starter doesn't impact electronics and communication.

As @SmallCrawler said, always replace Main & Aux at the same time. They work as a pair and need to be the same age and have the same wear.

I was having starting issues with mine and hopped on this website and did the Fuse 42 bypass. Everything seems fine until my girlfriend drives the Jeep and doesn’t hit the button to bypass the ESS and does short trips. The the ESS warning light comes on.

Should I replace the the AUX battery and put fuse 42 and the negative lead back?

Please explain why? Also is there a way to just prevent the ESS from coming on?

We have a 2019 XT5 we bought used. ESS does not have a button. The carfax showed it had 3 batteries replaced already. I bought a bypass device and the battery has been fine. I feel ESS is too hard on batteries and that Carfax confirmed it on the XT5.

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